Wall Street stock indexes edged down in volatile trading as markets around the world made a rough start to the week amid tensions on the Russia-Ukraine border. Here’s what we’re watching Monday:

• Cisco Systems has made a takeover offer worth more than $20 billion for software maker Splunk , according to people familiar with the matter, in what would be the networking giant’s biggest acquisition ever.
• Crown Resorts , one of Australia’s biggest casino operators, said Monday that it agreed to a $6.3 billion takeover by  Blackstone ,  following a roughly yearlong effort by the U.S. private-equity giant to acquire the company.

• Needham and Raymond James both trimmed their price targets for Avalara shares, but also kept their ratings of “buy” and “outperform” in place.
• The FDA on Friday authorized the use of a new Covid-19 antibody drug from Eli Lilly that retains effectiveness against the Omicron variant of the virus.
• Lockheed Martin on Sunday said it had scrapped plans to buy  Aerojet Rocketdyne Holdings after federal antitrust overseers last month sued to block the proposed $4.4 billion deal.
• Shares of Affirm Holdings were wavering in morning trading. The buy-now-pay-later company’s stock has closed down more than 20% in both of the past two sessions.
• Wedbush lifted its rating on Micron Technology to “outperform” and raised its price target for the stock to $120 from $100.
• Avis Budget ,   Advance Auto Parts  and  Arista Networks  are among the companies reporting earnings Monday.

Chart of the Day

• A turbulent start of the year for U.S. stocks has entered a new phase in recent days, with investors weighing good news about corporate earnings and the labor market against the stubborn challenges of high inflation, rising bond yields and geopolitical uncertainty.

Write to James Willhite at james.willhite@wsj.com