Riverbed SteelHead 5080, Руководство по установке и настройке

Страница: 54 / 94

54 | Troubleshooting
Packet ricochet: ICMP redirects
• Add static routes to LAN subnets through the LAN router.
• Enable in-path simplified routing.
Packet ricochet: ICMP redirects
These symptoms occur due to packet ricochet Internet Control Messaging Protocol (ICMP) redirects:
• Connections fail on the first attempt, but succeed on second attempt.
• On one or both sites, the in-path interface on the SteelHead is on a different network than the local
host.
• No in-path routes are defined.
Possible causes
• Traffic to the LAN is traveling to the WAN router on the way to the LAN, but the router drops the
packet.
• Outer connections to clients or servers are routed through the WAN interface to the WAN gateway
and then routed through the SteelHead to the next hop LAN gateway.
• The WAN router is probably dropping the SYN from the SteelHead before issuing an ICMP redirect.
Solutions
To resolve the packet ricochet ICMP redirects issue, do one of the following:
• Change the router ICMP configuration to forward the packet or turn off ICMP redirect.
• Change the in-path gateway to the LAN router.
• Add static routes to LAN subnets through the LAN router.
• Enable in-path simplified routing. For details, see “Simplified routing” on page 54 .
• Add in-path routes to local destinations to prevent the ICMP redirect and subsequent drop.
Simplified routing
Simplified routing changes the process used to select the destination Ethernet address for packets
transmitted from in-path interfaces.
Simplified routing collects the IP address for the next hop MAC address from each packet it receives to
address traffic. With simplified routing, you can use either the WAN-side or LAN-side device as a default
gateway. The SteelHead learns the right gateway to use by watching where the switch or router sends
the traffic, and by associating the next-hop Ethernet addresses with IP addresses. Enabling simplified
routing eliminates the need to add static routes when the SteelHead is in a different subnet from the
client and the server.