VLAN routing on layer 3 switch

Unanswered Question
Sep 10th, 2009

Hi, I set up 2 VLANs on a C4900 switch. VLAN A and B can ping each other.

When server1 from VLAN A sends a tcp Sync to server2 in VLAN B, server2 can get the packet and reply it back to server1, but server1 can't get that backbound packet.

I think it shouldn't be a problem when the vlans are on a layer 3 switch and the switch does the routing, is that correct? TIA.

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Overall Rating: 5 (1 ratings)
Edison Ortiz Thu, 09/10/2009 - 06:52

As long as you have ip routing enabled on the switch (you can verify this by typing show ip route and if the routing table is displayed you have routing running), the devices should be able to communicate with each other provided they have the correct IP Subnet and default gateway for their Vlan.



David Lin Thu, 09/10/2009 - 07:53

Edison, your comment absolutely clarified my doubt. Thanks a lot.

Jerry Ye Thu, 09/10/2009 - 06:57

NAT is not supported on the 4900 platform.



David Lin Thu, 09/10/2009 - 07:54

No, it doesn't support NAT.

And no ACL for these 2 vlans either.


ktwaddell Thu, 09/10/2009 - 07:40


Do you have any ACL's or are you doing any NATing on either vlan?




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