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Cisco2621 VLAN issue

I have successfully configured a VLAN on a Cisco 2621 router using the following settings:

interface FastEthernet 0/1.7

encapsulation dot1Q 7

ip address 192.168.7.1 255.255.255.0

interface FastEthernet 0/1.8

encapsulation dot1Q 8

ip address 192.168.8.1 255.255.255.0

Now I want to add a 3rd VLAN using the following settings:

interface FastEthernet 0/1.9

encapsulation dot1Q 9

ip address 172.16.30.1 255.255.0.0

After I added the 1.9 interface to the router, the 1.7 and the 1.8 interfaces continued to communicate between each other but neither could communicate with the 1.9 interface.

Is it possible to set up the router so that communication can exist in the manner I described above? Am I missing a step?

Thanks in advance.

5 REPLIES
Silver

Re: Cisco2621 VLAN issue

Hi ,

F0/1.7 and F0/1.8 belongs to same subnet so that they can communicate each other.Try to configure F0/1.9 in the same subnet of remaining interfaces and check whether you are able to ping or not ?

Blue

Re: Cisco2621 VLAN issue

actually, the above response is not correct.

the 1.7 and 1.8 are not on the same subnet as defined by the subnet mask.

(unless you were using bridging, the router would not let you configure two interfaces to the same subnet)

1.7 is subnet 192.168.7.0/24

1.8 is subnet 192.168.8.0/24

have you done a 'no shut' on the new 1.9 subInterface?

can a PC on 192.168.7.0 subnet ping 172.16.30.1?

can a PC on 192.168.8.0 subnet ping 172.16.30.1?

if so, perhaps you have a route table problem on the PC on 172.16.30.0/16 subnet. use the 'route print' command at the PC dos prompt to view the PCs routing table.

if you still have problems, please post the entire configuration if you can, minus any sensative public ip addresses and we can help you more. also provide a 'show ip route' so we can see exactly what the router knows about its routes.

New Member

Re: Cisco2621 VLAN issue

Thank you for your reply.

I did a 'no shut' on the 1.9 subinterface and that did not cure the problem.

I cannot ping 172.16.30.1 from either 1.7 or 1.8.

The following are the results of "show ip route" on the router:

C 192.168.8.0/24 is directly connected, FastEthernet0/1.8

C 172.16.0.0/16 is directly connected, FastEthernet0/1.9

10.0.0.0/30 is subnetted, 1 subnets

C 10.1.1.8 is directly connected, Serial0/0

C 192.168.7.0/24 is directly connected, FastEthernet0/1.7

"removed public IP" is subnetted, 1 subnets

C "removed publid IP" is directly connected, FastEthernet0/0

S* 0.0.0.0/0 [1/0] via 10.1.1.9

Purple

Re: Cisco2621 VLAN issue

I think the problem is with the switch on the far end , doesn't sound like the trunk is working right , you would have to post the entire switch config to take a look . On the switch on the far end did you create the layer 2 vlan and make sure it is allowed across the trunk ??? Usually on the router you have to specify one of the vlan subinterfaces as the native vlan and make sure that matches on the switch also for the trunk to work right . Don't see where you specified the native vlan in the router.

New Member

Re: Cisco2621 VLAN issue

I think I have found the problems.

1 - I had the incorrect IP address for the default gateway on the switch. After I entered the correct IP address, I was able to communicate between VLAN 9 and VLAN 7. I will not be able to test VLAN 8 until later on today but I think that it will work. Thank you everyone for your help.

2 - On the router, I did not have int 0/1.1 set up for trunking.

After I made these 2 changes, I was able to communicate between VLAN 9 and VLAN 7. I will not be able to test VLAN 8 until later on today but I think that it will work.

Thank you everyone for all of your help.

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