Summary Prospectus dated May 1, 2020

as revised March 1, 2021

Eaton Vance Core Bond Fund

Class /Ticker    A / EAGIX     I / EIGIX

This Summary Prospectus is designed to provide investors with key fund information in a clear and concise format. Before you invest, you may want to review the Fund’s Prospectus and Statement of Additional Information, which contain more information about the Fund and its risks. The Fund’s Prospectus and Statement of Additional Information, both dated May 1, 2020, as may be amended or supplemented, are incorporated by reference into this Summary Prospectus. For free paper or electronic copies of the Fund’s Prospectus, Statement of Additional Information, annual and semi-annual shareholder reports, and other information about the Fund, go to http://www.eatonvance.com/funddocuments, email a request to contact@eatonvance.com, call 1-800-262-1122, or ask any financial advisor, bank, or broker-dealer who offers shares of the Fund. Unless otherwise noted, page number references refer to the current Prospectus for this Fund.

Important Note. Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s annual and semi-annual shareholder reports will no longer be sent by mail unless you specifically request paper copies of the reports. Instead, the reports will be made available on the Fund’s website (http://www.eatonvance.com/funddocuments), and you will be notified by mail each time a report is posted and provided with a website address to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. If you are a direct investor, you may elect to receive shareholder reports and other communications from the Fund electronically by signing up for e-Delivery at eatonvance.com/edelivery. If you own your shares through a financial intermediary (such as a broker-dealer or bank), you must contact your financial intermediary to sign up.

You may elect to receive all future Fund shareholder reports in paper free of charge. If you are a direct investor, you can inform the Fund that you wish to continue receiving paper copies of your shareholder reports by calling 1-800-262-1122. If you own these shares through a financial intermediary, you must contact your financial intermediary or follow instructions included with this disclosure, if applicable, to elect to continue to receive paper copies of your shareholder reports. Your election to receive reports in paper will apply to all Eaton Vance funds held directly or to all funds held through your financial intermediary, as applicable.

Investment Objectives

The Fund's investment objectives are to seek current income and total return.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Investors may also pay commissions or other fees to their financial intermediary when they buy and hold shares of the Fund, which are not reflected below. You may qualify for a reduced sales charge on purchases of Class A shares if you invest, or agree to invest over a 13-month period, at least $50,000 in Eaton Vance funds. Certain financial intermediaries also may offer variations in Fund sales charges to their customers as described in Appendix A – Financial Intermediary Sales Charge Variations in the Fund's Prospectus. More information about these and other discounts is available from your financial intermediary and in Sales Charges beginning on page 27 of the Fund's Prospectus and page 22 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)	Class A	Class I
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%	None
Maximum Deferred Sales Charge (Load) (as a percentage of the lower of net asset value at purchase or redemption)	None	None

Annual Fund Operating Expenses (expenses you pay each year as a percentage of the value of your investment)(1)	Class A	Class I
Management Fees	0.45%	0.45%
Distribution and Service (12b-1) Fees	0.25%	None
Other Expenses	0.15%	0.15%
Total Annual Fund Operating Expenses	0.85%	0.60%
Expense Reimbursement(2)	(0.11)%	(0.11)%
Total Annual Fund Operating Expenses After Expense Reimbursement	0.74%	0.49%

⁽¹⁾ Expenses in the table above and the Example below reflect the expenses of the Fund and Core Bond Portfolio (the “Portfolio”), the Fund’s master Portfolio.

⁽²⁾ The administrator has agreed to reimburse the Fund’s expenses to the extent that Total Annual Fund Operating Expenses exceed 0.74% for Class A shares and 0.49% for Class I shares. This expense reimbursement will continue through April 30, 2021. Any amendment to or termination of this reimbursement would require approval of the Board of Trustees. The expense reimbursement relates to ordinary operating expenses only and does not include expenses such as: brokerage commissions, acquired fund fees and expenses of unaffiliated funds, borrowing costs (including borrowing costs of any acquired funds), taxes or litigation expenses. Amounts reimbursed may be recouped by the administrator during the same fiscal year to the extent actual expenses are less than the contractual expense cap during such year.

Example. This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, that the operating expenses remain the same and that any expense reimbursement arrangement remains in place for the contractual period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years	5 Years	10 Years
Class A shares	$547	$723	$914	$1,464
Class I shares	$50	$181	$324	$740

Portfolio Turnover

The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turn overs” the portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 89% of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objectives by investing primarily in fixed-income securities, which may include corporate bonds, U.S. Government securities, money market instruments, mortgage-backed securities (including collateralized mortgage obligations and so-called “seasoned” mortgage-backed securities), commercial mortgage-backed securities, asset-backed securities (including collateralized debt obligations and collateralized loan obligations) and convertible debt securities and other hybrid securities. The Fund may also invest in floating rate instruments, including loans. The Fund may invest significantly in securities issued by various U.S. Government-sponsored entities, such as the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association and Federal Home Loan Banks. Under normal market conditions, the Fund invests at least 80% of its net assets (plus any borrowings for investment purposes) in investment grade securities that are rated at least BBB by S&P Global Ratings (“S&P”) or by Fitch Ratings (“Fitch”) or Baa by Moody’s Investors Service, Inc. (“Moody’s”) or in unrated securities determined by the investment adviser to be of comparable quality (the “80% Policy”). The Fund limits investment in instruments rated below investment grade (including securities, loans and credit derivatives where the credit rating of the reference instrument is below investment grade) to not more than 15% of its total assets. Instruments rated below investment grade (sometimes referred to as “junk”) are rated below BBB by S&P or Fitch or Baa by Moody's or if unrated determined by the investment adviser to be of comparable quality. The Fund may invest in instruments in any rating category, including those in default. For purposes of rating restrictions, if instruments are rated differently by two or more rating agencies, the highest rating is used. The Fund is expected to have an average effective maturity between five and ten years.

The Fund may invest up to 25% of its total assets in foreign securities, some of which may be issued by issuers domiciled in emerging market countries. As an alternative to holding foreign securities directly, the Fund may invest in U.S. dollar-denominated securities of foreign companies that trade on U.S. exchanges or in the over-the-counter market (including depositary receipts that evidence ownership in underlying foreign securities). The Fund may invest a portion of its assets in Eurodollar and Yankee Dollar Instruments. The Fund may, at times, engage in derivative transactions (such as options, swaptions, interest rate swaps, forward rate contracts, futures contracts and options thereon, forward foreign currency exchange contracts and credit derivatives) to seek to hedge against fluctuations in securities prices, interest rates or currency exchange rates, to seek to enhance returns or as a substitute for purchasing or selling securities or currencies. Permitted credit derivatives include credit default swaps, total return swaps and credit options. There is no stated limit on the Fund’s use of derivatives. The Fund may invest in restricted securities and may purchase securities on a when-issued basis and for future delivery by means of “forward commitments.” The Fund may invest up to 10% of its net assets in inflation-linked debt securities. The Fund may also invest up to 10% of its net assets in municipal securities directly or through investments in other investment companies.

Investment decisions for the Fund are made primarily on the basis of fundamental and quantitative research conducted by the investment adviser’s research staff, including macroeconomic analysis and bottom-up credit research. Management of the Fund involves consideration of numerous factors (such as quality of business franchises, financial strength, management capability and integrity, growth potential, valuation and earnings and cash flow capabilities). The portfolio manager(s) may also consider financially material environmental, social and governance factors in evaluating an issuer. These considerations may be taken into account alongside other fundamental research in the investment selection process. The portfolio managers may sell a security when the

Eaton Vance Core Bond Fund 2 Summary Prospectus dated May 1, 2020 as revised March 1, 2021

investment adviser’s valuation target is reached, the fundamentals of the company change or to pursue more attractive investment options. The portfolio managers intend to focus on risk management and also seek to preserve capital to the extent consistent with the Fund’s investment objectives. The portfolio managers may also use sector rotation strategies in their management of the Fund. The Fund intends to seek to manage investment risk by maintaining broad issuer and industry diversification among its holdings, and by utilizing fundamental analysis of risk/return characteristics in securities selection.

The Fund currently invests its assets in the Portfolio, a separate registered investment company with the same investment objectives as the Fund.

Principal Risks

Market Risk. The value of investments held by the Fund may increase or decrease in response to economic, political, financial or other disruptive events (whether real, expected or perceived) in the U.S. and global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in reaction to changing market conditions. Monetary and/or fiscal actions taken by U.S. or foreign governments to stimulate or stabilize the global economy may not be effective and could lead to high market volatility. No active trading market may exist for certain investments held by the Fund, which may impair the ability of the Fund to sell or to realize the current valuation of such investments in the event of the need to liquidate such assets.

Interest Rate Risk. In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise. Duration measures a fixed-income security’s price sensitivity to changes in the general level of interest rates. Generally, securities with longer durations or maturities are more sensitive to changes in interest rates than securities with shorter durations or maturities, causing them to be more volatile. Conversely, fixed-income securities with shorter durations or maturities will be less volatile but may provide lower returns than fixed-income securities with longer durations or maturities. In a rising interest rate environment, the duration of income securities that have the ability to be prepaid or called by the issuer may be extended. In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate. Certain instruments held by the Fund pay an interest rate based on the London Interbank Offered Rate (“LIBOR”), which is the average offered rate for various maturities of short-term loans between certain major international banks. LIBOR is expected to be phased out by the end of 2021. While the effect of the phase out cannot yet be determined, it may result in, among other things, increased volatility or illiquidity in markets for instruments based on LIBOR and changes in the value of such instruments.

Credit Risk. Investments in fixed-income and other debt obligations (referred to below as “debt instruments”) are subject to the risk of non-payment of scheduled principal and interest. Changes in economic conditions or other circumstances may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults. Such non-payments and defaults may reduce the value of Fund shares and income distributions. The value of debt instruments also may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, the Fund could experience delays or limitations with respect to its ability to realize the benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar situation, the Fund may be required to retain legal or similar counsel, which may increase the Fund’s operating expenses and adversely affect net asset value.

U.S. Government Securities Risk. Although certain U.S. Government-sponsored agencies (such as the Federal Home Loan Mortgage Corporation and the Federal National Mortgage Association) may be chartered or sponsored by acts of Congress, their securities are neither issued nor guaranteed by the U.S. Treasury. U.S. Treasury securities generally have a lower return than other obligations because of their higher credit quality and market liquidity.

Money Market Instrument Risk. Money market instruments may be adversely affected by market and economic events, such as a sharp rise in prevailing short-term interest rates; adverse developments in the banking industry, which issues or guarantees many money market instruments; adverse economic, political or other developments affecting issuers of money market instruments; changes in the credit quality of issuers; and default by a counterparty.

Mortgage- and Asset-Backed Securities Risk. Mortgage- and asset-backed securities represent interests in “pools” of commercial or residential mortgages or other assets, including consumer loans or receivables. Movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain types of mortgage- and asset-backed securities. Although certain mortgage- and asset-backed securities are guaranteed as to timely payment of interest and principal by a government entity, the market price for such securities is not guaranteed and will fluctuate. The purchase of mortgage- and asset-backed securities issued by non-government

Eaton Vance Core Bond Fund 3 Summary Prospectus dated May 1, 2020 as revised March 1, 2021

entities may entail greater risk than such securities that are issued or guaranteed by a government entity. Mortgage- and asset-backed securities issued by non-government entities may offer higher yields than those issued by government entities, but may also be subject to greater volatility than government issues and can also be subject to greater credit risk and the risk of default on the underlying mortgages or other assets. Investments in mortgage- and asset-backed securities are subject to both extension risk, where borrowers pay off their debt obligations more slowly in times of rising interest rates, and prepayment risk, where borrowers pay off their debt obligations sooner than expected in times of declining interest rates.

Convertible and Other Hybrid Securities Risk. Convertible and other hybrid securities (including preferred and convertible instruments) generally possess certain characteristics of both equity and debt securities. In addition to risks associated with investing in income securities, such as interest rate and credit risks, hybrid securities may be subject to issuer-specific and market risks generally applicable to equity securities. Convertible securities may also react to changes in the value of the common stock into which they convert, and are thus subject to equity investing and market risks. A convertible security may be converted at an inopportune time, which may decrease the Fund’s return.

Lower Rated Investments Risk. Investments rated below investment grade and comparable unrated investments (sometimes referred to as “junk”) have speculative characteristics because of the credit risk associated with their issuers. Changes in economic conditions or other circumstances typically have a greater effect on the ability of issuers of lower rated investments to make principal and interest payments than they do on issuers of higher rated investments. An economic downturn generally leads to a higher non-payment rate, and a lower rated investment may lose significant value before a default occurs. Lower rated investments typically are subject to greater price volatility and illiquidity than higher rated investments.

Foreign Investment Risk. Foreign investments can be adversely affected by political, economic and market developments abroad, including the imposition of economic and other sanctions by the United States or another country. Foreign markets may be smaller, less liquid and more volatile than the major markets in the United States and, as a result, Fund share values may be more volatile. Trading in foreign markets typically involves higher expense than trading in the United States. The Fund may have difficulties enforcing its legal or contractual rights in a foreign country. Depositary receipts are subject to many of the risks associated with investing directly in foreign instruments.

Emerging Markets Investment Risk. Investment markets within emerging market countries are typically smaller, less liquid, less developed and more volatile than those in more developed markets like the United States, and may be focused in certain economic sectors. Emerging market securities often involve greater risks than developed market securities.

Currency Risk. Exchange rates for currencies fluctuate daily. The value of foreign investments may be affected favorably or unfavorably by changes in currency exchange rates in relation to the U.S. dollar. Currency markets generally are not as regulated as securities markets and currency transactions are subject to settlement, custodial and other operational risks.

Derivatives Risk. The Fund’s exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. The use of derivatives can lead to losses because of adverse movements in the price or value of the security, instrument, index, currency, commodity, economic indicator or event underlying a derivative (“reference instrument”), due to failure of a counterparty or due to tax or regulatory constraints. Derivatives may create leverage in the Fund, which represents a non-cash exposure to the underlying reference instrument. Leverage can increase both the risk and return potential of the Fund. Derivatives risk may be more significant when derivatives are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position held by the Fund. Use of derivatives involves the exercise of specialized skill and judgment, and a transaction may be unsuccessful in whole or in part because of market behavior or unexpected events. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying reference instrument. Derivative instruments traded in over-the-counter markets may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying reference instrument. If a derivative’s counterparty is unable to honor its commitments, the value of Fund shares may decline and the Fund could experience delays in the return of collateral or other assets held by the counterparty. The loss on derivative transactions may substantially exceed the initial investment, particularly when there is no stated limit on the Fund’s use of derivatives. A derivative investment also involves the risks relating to the reference instrument underlying the investment.

Restricted Securities Risk. Unless registered for sale to the public under applicable federal securities law, restricted securities can be sold only in private transactions to qualified purchasers pursuant to an exemption from registration. The sale price realized from a private transaction could be less than the Fund’s purchase price for the restricted security. It may be difficult to identify a qualified purchaser for a restricted security held by the Fund and such security could be deemed illiquid. It may also be more difficult to value such securities.

Eaton Vance Core Bond Fund 4 Summary Prospectus dated May 1, 2020 as revised March 1, 2021

Liquidity Risk. The Fund is exposed to liquidity risk when trading volume, lack of a market maker or trading partner, large position size, market conditions, or legal restrictions impair its ability to sell particular investments or to sell them at advantageous market prices. Consequently, the Fund may have to accept a lower price to sell an investment or continue to hold it or keep the position open, sell other investments to raise cash or abandon an investment opportunity, any of which could have a negative effect on the Fund’s performance. These effects may be exacerbated during times of financial or political stress.

Additional Risks of Loans. Loans are traded in a private, unregulated inter-dealer or inter-bank resale market and are generally subject to contractual restrictions that must be satisfied before a loan can be bought or sold. These restrictions may impede the Fund’s ability to buy or sell loans (thus affecting their liquidity) and may negatively impact the transaction price. See also “Market Risk” above. It also may take longer than seven days for transactions in loans to settle. Due to the possibility of an extended loan settlement process, the Fund may hold cash, sell investments or temporarily borrow from banks or other lenders to meet short-term liquidity needs, such as to satisfy redemption requests from Fund shareholders. The types of covenants included in loan agreements generally vary depending on market conditions, the creditworthiness of the issuer, the nature of the collateral securing the loan and possibly other factors. Loans with fewer covenants that restrict activities of the borrower may provide the borrower with more flexibility to take actions that may be detrimental to the loan holders and provide fewer investor protections in the event of such actions or if covenants are breached. The Fund may experience relatively greater realized or unrealized losses or delays and expense in enforcing its rights with respect to loans with fewer restrictive covenants. Loans to entities located outside of the U.S. may have substantially different lender protections and covenants as compared to loans to U.S. entities and may involve greater risks. The Fund may have difficulties and incur expense enforcing its rights with respect to non-U.S. loans and such loans could be subject to bankruptcy laws that are materially different than in the U.S. Loans may be structured such that they are not securities under securities law, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. Loans are also subject to risks associated with other types of income investments, including credit risk and risks of lower rated investments.

When-Issued and Forward Commitment Risk. Securities purchased on a when-issued or forward commitment basis are subject to the risk that when delivered they will be worth less than the agreed upon payment price.

Inflation-Linked Investments Risk. Inflation-linked investments are subject to the effects of changes in market interest rates caused by factors other than inflation (real interest rates). In general, the price of an inflation-linked investment tends to decrease when real interest rates increase and increase when real interest rates decrease. Interest payments on inflation-linked investments may vary widely and will fluctuate as the principal and interest are adjusted for inflation. Any increase in the principal amount of an inflation-linked investment will be considered taxable ordinary income, even though the Fund will not receive the principal until maturity. There can be no assurance that the inflation index used will accurately measure the real rate of inflation in the prices of goods and services. The Fund’s investments in inflation-linked investments may lose value in the event that the actual rate of inflation is different from the rate of the inflation index.

Municipal Obligations Risk. The amount of public information available about municipal obligations is generally less than for corporate equities or bonds, meaning that the investment performance of municipal obligations may be more dependent on the analytical abilities of the investment adviser than stock or corporate bond investments. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund’s ability to sell its municipal obligations at attractive prices. The differences between the price at which an obligation can be purchased and the price at which it can be sold may widen during periods of market distress. Less liquid obligations can become more difficult to value and be subject to erratic price movements. The increased presence of nontraditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume.

Pooled Investment Vehicles Risk. Pooled investment vehicles are open- and closed-end investment companies and exchange-traded funds (“ETFs”). Pooled investment vehicles are subject to the risks of investing in the underlying securities or other investments. Shares of closed-end investment companies and ETFs may trade at a premium or discount to net asset value and are subject to secondary market trading risks. In addition, the Fund will bear a pro rata portion of the operating expenses of a pooled investment vehicle in which it invests.

Leverage Risk. Certain Fund transactions may give rise to leverage. Leverage can result from a non-cash exposure to the underlying reference instrument. Leverage can increase both the risk and return potential of the Fund. The Fund is required to segregate liquid assets or otherwise cover the Fund’s obligation created by a transaction that may give rise to leverage. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet segregation requirements. Leverage may cause the Fund’s share price to be more volatile than if it had not been leveraged, as certain types of leverage may exaggerate the effect of any increase or decrease in the value of the Fund’s portfolio securities. The loss on leveraged investments may substantially exceed the initial investment.

Eaton Vance Core Bond Fund 5 Summary Prospectus dated May 1, 2020 as revised March 1, 2021

Portfolio Turnover Risk. The annual portfolio turnover rate of the Fund may exceed 100%. A mutual fund with a high turnover rate (100% or more) may generate more capital gains and may involve greater expenses (which may reduce return) than a fund with a lower rate. Capital gains distributions will be made to shareholders if offsetting capital loss carry forwards do not exist.

Risks Associated with Active Management. The success of the Fund’s investment strategy depends on portfolio management’s successful application of analytical skills and investment judgment. Active management involves subjective decisions.

General Fund Investing Risks. The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objectives. It is possible to lose money by investing in the Fund. The Fund is designed to be a long-term investment vehicle and is not suited for short-term trading. Investors in the Fund should have a long-term investment perspective and be able to tolerate potentially sharp declines in value. Purchase and redemption activities by Fund shareholders may impact the management of the Fund and its ability to achieve its investment objective(s). In addition, the redemption by one or more large shareholders or groups of shareholders of their holdings in the Fund could have an adverse impact on the remaining shareholders in the Fund. The Fund relies on various service providers, including the investment adviser, in its operations and is susceptible to operational, information security and related events (such as cyber or hacking attacks) that may affect the service providers or the services that they provide to the Fund. An investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance

The following bar chart and table provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and how the Fund’s average annual returns over time compare with those of a broad-based securities market index. The returns in the bar chart are for Class A shares and do not reflect a sales charge. If the sales charge was reflected, the returns would be lower. Past performance (both before and after taxes) is not necessarily any indication of how the Fund will perform in the future. The Fund’s performance reflects the effects of expense reductions. Absent these reductions, performance would have been lower. Updated Fund performance information can be obtained by visiting www.eatonvance.com.

For the ten years ended December 31, 2019, the highest quarterly total return for Class A was 3.50% for the quarter ended March 31, 2019 and the lowest quarterly return was -3.10% for the quarter ended December 31, 2016.

Average Annual Total Return as of December 31, 2019	One Year	Five Years	Ten Years
Class A Return Before Taxes	3.86%	1.89%	3.20%
Class A Return After Taxes on Distributions	2.49%	0.70%	1.77%
Class A Return After Taxes on Distributions and Sale of Class A Shares	2.27%	0.86%	1.87%
Class I Return Before Taxes	9.29%	3.15%	3.94%
Bloomberg Barclays U.S. Aggregate Bond Index (reflects no deductions for fees, expenses or taxes)	8.72%	3.05%	3.74%

These returns reflect the maximum sales charge for Class A (4.75%). Investors cannot invest directly in an Index.

After-tax returns are calculated using the highest historical individual federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on a shareholder’s tax situation and the actual characterization of distributions, and may differ from those shown. After-tax returns are not relevant to shareholders who hold shares in tax-deferred accounts or to shares held by non-taxable entities. After-tax returns for other Classes of shares will vary from the after-tax returns presented for Class A shares. Return After Taxes on Distributions for a period may be the same as Return Before Taxes for that period because no taxable distributions were made during that period. Also, Return After Taxes on Distributions and Sale of Fund Shares for a period may be greater than or equal to Return Before Taxes and/or Return After Taxes on Distributions for the same period because of losses realized on the sale of Fund shares.

Eaton Vance Core Bond Fund 6 Summary Prospectus dated May 1, 2020 as revised March 1, 2021

Management

Investment Adviser. Boston Management and Research (“BMR”) serves as investment adviser to the Portfolio. Effective March 1, 2021, Eaton Vance Management (“Eaton Vance”) serves as investment adviser to the Fund.

Portfolio Managers

Vishal Khanduja, CFA, Vice President of Eaton Vance and BMR, has managed the Portfolio since June 2017 and the Fund since March 1, 2021.

Brian S. Ellis, CFA, Vice President of Eaton Vance and BMR, has managed the Portfolio since June 2017 and the Fund since March 1, 2021.

Purchase and Sale of Fund Shares

You may purchase, redeem or exchange Fund shares on any business day, which is any day the New York Stock Exchange is open for business. You may purchase, redeem or exchange Fund shares either through your financial intermediary or directly from the Fund either by writing to the Fund, P.O. Box 9653, Providence, RI 02940-9653, or by calling 1-800-262-1122. The minimum initial purchase or exchange into the Fund is $1,000 for Class A and $250,000 for Class I (waived in certain circumstances). There is no minimum for subsequent investments.

Tax Information

If your shares are held in a taxable account, the Fund’s distributions will be taxed to you as ordinary income and/or capital gains, unless you are exempt from taxation. If your shares are held in a tax-advantaged account, you will generally be taxed only upon withdrawals from the account.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase the Fund’s shares through a broker-dealer or other financial intermediary (such as a bank) (collectively, “financial intermediaries”), the Fund, its principal underwriter and its affiliates may pay the financial intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the financial intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

4472  3.1.21 © 2021 Eaton Vance Management

Eaton Vance Core Bond Fund 7 Summary Prospectus dated May 1, 2020 as revised March 1, 2021