Inter-vlan routing issue on 3750

Unanswered Question
Jun 2nd, 2009

I have a catalyst switch c3750 which i want to do vlan with it. I have vlan 1 and 2 on it.

Vlan 1 ip addr

vlan 2 ip addr

And i tag each port to each vlan, port 1 and 2 precise.I then have host A ip addr to be gateway mask /24. Host B gateway mask/24.

The issue is that Host A can ping the default-gateway of host B ( but can ping host B But Host B can ping the default-gateway of host A( but can not ping host A

Pls help

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Richard Burts Tue, 06/02/2009 - 06:21

I wonder if there is a typo mistake in your post. You say:"The issue is that Host A can ping the default-gateway of host B ( but can ping host B". If it is a problem it seems there should be a "not ping host B". Can you clarify.

I have looked at the config that you posted and it does not have any obvious problems. I can think of 2 possible explanations for the problem:

- there is a problem with the configuration of the PCs and either the address, the mask, or the default gateway is not configured as your post says that they are.

- or the PCs have an active firewall and the firewall is not allowing the ping.



princesegunloves Tue, 06/02/2009 - 07:40

Sorry for the error in the post.What am i mean was that the two host can ping the two vlan ip addr. But host A cannot ping host B. After ur post now i remove the firewall on both machine but the issue is the same. But the switch can ping both hosts.

I intended putting a router which i did but the situation remain the same. The ping is not bi-direction its one way.

( by config router-on-a-stick)

Edison Ortiz Tue, 06/02/2009 - 08:43

Please provide the IPCONFIG /ALL output from both hosts and go back to the 3750 inter-vlan design configuration.



Edison Ortiz Tue, 06/02/2009 - 06:34

The config posted looks good and per your description, the bi-directional ping should work.

Have you verified the workstations have any firewall disabled?



Richard Burts Tue, 06/02/2009 - 08:45

The configuration of the router is doing just what the switch was doing when you had IP addresses and routing enabled on the switch. So I am not surprised that the situation continues, since I did not believe that the problem was on the switch.

I am not clear about an aspect of your post so I will ask a question: can the PC at ping the interface at

Another question: if you do extended ping (on the switch if the IP addresses are on the switch or on the router if the addresses have been moved to the router) and in the extended ping specify the source address as the address of the other vlan, does the ping work? (if you ping the PC and specify the source address as does the ping work?



princesegunloves Wed, 06/03/2009 - 00:42

The PC at can ping the interface and also the PC at can ping the interface on

NO. From PC if i ping PC it does not ping or work.

This is the ipconfig/all on both PC

IP Address. . . . . . . . . . . . :

Subnet Mask . . . . . . . . . . . :

Default Gateway . . . . . . . . . :

and PCB

IP Address. . . . . . . . . . . . :

Subnet Mask . . . . . . . . . . . :

Default Gateway . . . . . . . . . :

And all firewall is being disable

thotsaphon Mon, 06/15/2009 - 05:39


Did you connect the switch to the router by using the trunk port?

Did you already have in the vlan database?

Please post a "show ip route" command on the router.


princesegunloves Fri, 06/19/2009 - 05:05


I did i connected the to the router on a truck port. I have vlan 2 encap on the router.

When i should ip route. it should that we have two direct connected which is vlan1 N VALN2.


Thanks to everybody..


This Discussion