interVLAN routing problem

[kmigmar805]

Dear Experts,

I am trying to setup intervlan configuration and stuck on a problem. Here are the details:

1. Switches Catalyst 3750-x (as core switch) and Catalyst 2960S (as access switch)

2. Both switches have VLAN 20 and VLAN 1 on their database and both are active. BTW, after I figure out how to properly configure interVLAN routing the native VLAN 1 will not be used anymore. This is just an initial test.

3. VLAN 20 SVI interface (IP 192.168.20.200) on 3750 is up and can be pinged from catalyst 2960.

4. VLAN 1 SVI interface (IP 192.168.170.200) on 3750 is up and also can be pinged from

Catalyst  2960.

5. Catalyst 3670 can ping a client computer (IP 192.168.20.10) connected to Catalyst 2960.

6.  IP route enabled on 3750

7. Trunking is enabled on etherchannel connecting both 3750 and 2960

8. Client computer in VLAN 20 (connected to 2960) can ping VLAN 20 SVI interface 192.168.20.200 on switch 3560.

But, the client computer in VLAN 20 can not reach any computer in VLAN 1 and vice versa. Strangely, the switches which these computers are connected to can ping each other or any connected client copmuters without any problem as described above.

Please kindly help me on this issue.

Thank you so much!

[Leo Laohoo]

Configuring Inter-VLAN Routing with Catalyst 3750 Series Switches

[kmigmar805]

Thank you very much for the prompt reply! Really appreciate it.

Upon further investigation, it turns out the problem root is in classless subnet mask of one of VLANs. All other VLANs with /24 mask are communicating fine between each other.

VLAN1 at this point have /22 mask. I have enabled CIDR routing in the 3750-X with 'ip classless' command in global config mode. But, it is still not routing between  VLAN1 with /22 mask  and  other VLANS with /24 masks.

Could anyone adivse on how to enable CIDR routing in Catalyst 3750-x?

Thanks a lot!

.

[glen.grant · Accepted solution]

   The mask should not have anything to do with your issue.  The pc clients in vlan 1 , do they have the correct mask and their default gateway  pointed at the vlan 1 SVI on the 3750 ?  Firewalls on the pc's turned off ?   Sounds like a gateway issue if you can reach them from the directly attached switch . 

[John Blakley · Accepted solution]

I agree with Glen. It's not a problem that you have mixed subnets in your switch. Can you ping the SVI from one of the "classful" /24 subnet PCs? If so, your switch is routing correctly and it points back to your PCs either not having the correct mask or their default gateway is incorrect.

HTH,

John

[Leo Laohoo · Accepted solution]

 Upon further investigation, it turns out the problem root is in classless subnet mask of one of VLANs. All other VLANs with /24 mask are communicating fine between each other. 


VLAN1 at this point have /22 mask. I have enabled CIDR routing in the 3750-X with 'ip classless' command in global config mode. But, it is still not routing between  VLAN1 with /22 mask  and  other VLANS with /24 masks

You're barking the wrong tree.

Please post your config.

[kmigmar805]

Dear Experts,

I tremendously appreciate your help! It was indeed incorrectly set gateway issue. You guys are brilliant. Now both classful and CIDR VLANs are talking to each other. Thank you so much!

Unfortunately, I have a new problem. Computers in VLAN 20 are now getting IP address meant for different VLAN (lets say for VLAN30). The ip helper seems to be working ok  and getting IP from DHCP. But, only for wrong VLAN with wrong gateway address etc.

I am using Win 2k8 R2 DHCP server and configured a new scope for VLAN 20. On the Scope Options I have added SVI interface IP address for default router for this scope. But, for some  reason computers in VLAN 20 got IP for VLAN 30... what am I doing incorrectly ?

Thanks a million in advance!

[Leo Laohoo]

Please post your config.

[Sebastian Helmer · Accepted solution]

I guess u enabled "ip routing" in the config mode already?

What does "sh up route" shows u?

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