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Cisco Bug: CSCvv26343 - Having 2x interfaces share one routing table can create asymmetrical routing issues.

Last Modified

Aug 19, 2020

Products (1)

  • Cisco TelePresence Video Communication Server (VCS)

Known Affected Releases


Description (partial)

Currently on Expressway we only use a single routing table even when you're using a dual-interface Exp-E server, and this can cause a few potential asymmetrical routing scenarios depending on src/dst IP addresses for the connections. However, if we moved to policy based routing with per interface routing tables we could alleviate most of these issues.

Scenario 1) You are an admin who wants connectivity to both interfaces of the Exp-E from a single computer for testing and management purposes. 
- Currently, each source address will only be able to connect to a single interface on the Exp-E due to the static routing, but if we changed to policy based routing we can make a per interface routing table to allow the exp-e to intelligently respond to a HTTP, ICMP, SIP, etc. requests from the originating interface for the connection. 

Scenario 2) If you factory reset (manually or due to clustering changes) a Dual-NIC Exp-E then it will revert the Dual-NIC setting, and this can cause routing failures and martian packet errors if the default gateway was for interface LAN2/eth1 requiring console access to recover. 
- If we used policy based routing we would have a default gateway configured for both interfaces, and we can then make sure that main route table only includes the gateway for active interfaces.
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