Alcatel Carrier Internetworking Solutions 8800 User Manual
Troubleshooting IP Routing
Introduction
OmniSwitch Troubleshooting Guide
September 2005
page 12-3
Introduction
The primary function of IP Routing is processing Layer 3 IP packets and forwarding them in between two
different networks or subnets. This is broken down into two functions. First is determining the best path to
get from one network or subnet to the next and second is to forwarding the packet into that destination
network.
different networks or subnets. This is broken down into two functions. First is determining the best path to
get from one network or subnet to the next and second is to forwarding the packet into that destination
network.
With that being said you need to figure out what type of routing the client is doing. This section will only
go over basic IP Routing. If the client is using an advanced routing protocol such as OSPF, VRRP, RIP II,
etc., please refer to the appropriate sections in the index.
go over basic IP Routing. If the client is using an advanced routing protocol such as OSPF, VRRP, RIP II,
etc., please refer to the appropriate sections in the index.
Note. This document does not discuss the basic operation of IP. To learn about how IP works, refer to the
“Configuring IP” chapter in the appropriate OmniSwitch Network Configuration Guide.
“Configuring IP” chapter in the appropriate OmniSwitch Network Configuration Guide.
IP Routing Protocol Failure
A failure of IP Routing would be a particular device that is unable to get out of the network; you will have
problems getting to a different subnet.
problems getting to a different subnet.
Troubleshooting via the CLI
If devices in different VLANs cannot communicate, we have a routing failure. The first thing to do is
verify the IP setup of the devices in question to make sure they are correct; check for IP address, subnet
mask, and default gateway address on both devices.
verify the IP setup of the devices in question to make sure they are correct; check for IP address, subnet
mask, and default gateway address on both devices.
If the devices can communicate within their respective VLANs, but not outside of the VLAN, verify the
default gateway is correct for the subnet, and try pinging it. If it responds, the device should be able to get
out of its VLAN without issue.
default gateway is correct for the subnet, and try pinging it. If it responds, the device should be able to get
out of its VLAN without issue.
The next step is to ping the gateway to the destination VLAN. Assuming the Falcon is doing the routing
for the VLANs, this address will show in the output of a show vlan router ip command.
for the VLANs, this address will show in the output of a show vlan router ip command.
-> show vlan router ip
vlan ip address ip mask encap mode oper mtu
------+-----------------+-----------------+---------+---------+------+-----
1
------+-----------------+-----------------+---------+---------+------+-----
1
192.168.001.001 255.255.255.000 e2 forward on 1500
2
192.168.002.001 255.255.255.000 e2 forward off 1500
If the address does not respond to a ping, verify that a port in the VLAN is forwarding via the
show vlan port command. Without an active port in a VLAN, the router instance is not active and
will not respond to pings.
show vlan port command. Without an active port in a VLAN, the router instance is not active and
will not respond to pings.
-> show vlan 1 port
port type status
--------+---------+--------------
1/1
--------+---------+--------------
1/1
default inactive
1/2
default inactive
1/3
default inactive