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rspan problem

rahil khan
Level 1
Level 1

I have build topology like this:

host------c2950(f0/3)------(f0/4)c3550(f0/41)----modem-----Internet

I wanted to monitor c3560 port where modem is connected from host. So for that I configured rspan. configurate show below. But problem is that after configuration f0/4 of c3550 remains up and f0/3 of c2950 goes down. WHen I look at status of f0/4 it show "FastEthernet0/4 is up, line protocol is down (monitoring)". I tried to search websites It seems configuration is fine. Kindly help.

on c3550:

interface FastEthernet0/4

switchport trunk encapsulation dot1q

switchport mode trunk

switchport nonegotiate

interface FastEthernet0/41

switchport mode dynamic desirable

spanning-tree portfast

monitor session 2 destination interface Fa0/8

monitor session 2 source remote vlan 20

interface FastEthernet0/9

switchport mode access

spanning-tree portfast

spanning-tree guard loop

end

interface FastEthernet0/3

switchport mode trunk

switchport nonegotiate

spanning-tree guard loop

ip dhcp snooping trust

end

monitor session 1 source interface Fa0/41

monitor session 1 destination remote vlan 20 reflector-port Fa0/4

on c2950:

monitor session 2 destination interface Fa0/9
monitor session 2 source remote vlan 20

interface FastEthernet0/9
switchport mode access
spanning-tree portfast
spanning-tree guard loop
end

interface FastEthernet0/3
switchport mode trunk
switchport nonegotiate
spanning-tree guard loop
ip dhcp snooping trust
end

1 Reply 1

Amit Aneja
Level 3
Level 3

Rahil,

Here is the problem, the port fa4 is a trunk port & a trunk port cannot be configured as reflector port. so, what you are seeing is expected.

When you configure a switch port as a reflector port, it is no longer a normal switch port; only looped-back traffic passes through the reflector port.

The reflector ports should not have any physical connection and should remain vacant.

If you have a free port available on 3550, configure it as a reflector & things should work fine.

Also, make sure that you have RSPAN vlan configured on both the switches.

Ref Guide:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_19_ea1/configuration/guide/swspan.html#wp1073772

Regards,

Amit Aneja

Review Cisco Networking products for a $25 gift card