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New Member

IRB Feature on Cisco 2621 with a Trunk to a Catalyst 3550


i have a problem with a Catalyst 3550 and a Cisco 2621 connected over a trunk. On the Router is IRB configured to bridge betwen two Vlans and two route between the other. Here the relevant configuration:

ROUTER 2621 Configuration

bridge irb

interface FastEthernet0/1


no ip address

speed 100


interface FastEthernet0/0.21

encapsulation isl 21

ip address

no ip redirects

interface FastEthernet0/0.22

encapsulation isl 22

no ip redirects

bridge-group 66

interface FastEthernet0/0.23

encapsulation isl 23

no ip redirects

bridge-group 66

interface BVI66

ip address

bridge 66 protocol ieee

bridge 66 route ip

CATALYST 3550 Configuration

interface FastEthernet0/6

description TRUNK TO LANR001 FAS 0/1

switchport trunk encapsulation isl

switchport mode trunk

no ip address

duplex full

speed 100

interface Vlan23

ip address

When i try to reach the Catalyst from an station in VLAN 22 with ip address it doesn't work, same when i try to reach the station from the switch. The only station where it works ist the Cisco 2621 with the trunk.

Same configuration on a Catalyst 5000 works.

Any help welcome!!



Re: IRB Feature on Cisco 2621 with a Trunk to a Catalyst 3550

Is your station plugged into a port on the 3550 in VLAN22 ?

Can you do a show int fa0/6 switchport and paste results here?

If you have the EMI image on the 3550 you can set up a interface vlan22 as well and route for all the VLANs.

New Member

Re: IRB Feature on Cisco 2621 with a Trunk to a Catalyst 3550

Yes the station is plugged into to a port on he 3550 VLAN22.

Here ist the show output:

CAT3550#sh int fas 0/6 switchport

Name: Fa0/6

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: isl

Operational Trunking Encapsulation: isl

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Operational private-vlan: none

Trunking VLANs Enabled: ALL

Pruning VLANs Enabled: 2-1001

Protected: false

Unknown unicast blocked: disabled

Unknown multicast blocked: disabled

Voice VLAN: none (Inactive)

Appliance trust: none

I know that i can route betwenn VLANs with the EMI image, but the SMI image is running. The other point is why it works with a Catalyst 5000 and not with the 3550?