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Managing a 3750

I have two 3750's connected to each other via a 802.1q trunk link. On Switch_A interface Gi 1/0/4 connects to Switch_B GI 1/0/1. Switch_ A is the VTP Server, and Switch_ B is a VTP client.

All ports fa 1/0/1 - 48 are assigned to the Data vlan (100) on both switches.

On Switch_A int GI 1/0/1 is configured as a routed interface and connects to a 6500 over 10mbps EAD circuit.  Switch_B has no direct connection back to the 6500, apart from the trunk link back to Switch_A.

Switch_A has IP routing enabled and a route of 0.0.0.0 0.0.0.0 172.30.100.202 over the routed interface (172.30.100.201/30 assigned to the routed interface).

VLAN100 on Switch_A has an IP address (192.168.10.254/24) and is accessible from hosts connected to the 6500

Switch_B also has an IP address on VLAN100 (192.168.10.253/24) this is not accessible via hosts on the 6500, however it is accessible from Switch_A.

both switches have a a route 0.0.0.0 0.0.0.0 172.30.100.202 (100.202 being the interface on the 6500) configured and both have IP routing enabled.

Can anyone assist in why i can not either telnet or ping VLAN100 on Switch_B.

Regards

Jeff

  • LAN Switching and Routing
1 ACCEPTED SOLUTION

Accepted Solutions
Bronze

Managing a 3750

Hi Jeff,

Try putting ip default-gateway on Switch2, pointing to Switch1's VLAN100 IP address.

Nick

4 REPLIES

Managing a 3750

Based on the above, switch B does not have a route to the gateway you assigned. Change switch B's gateway to something on its subnet (switch A SVI). Remember that the gateway must be in the same subnet as the device. Switch a is okay because it has an interface in the 172x.x.x network and therefore has a connected route. However, connected devices in VLAN100 would need to use A's SVI a the gateway.

Bronze

Managing a 3750

Hi Jeff,

Try putting ip default-gateway on Switch2, pointing to Switch1's VLAN100 IP address.

Nick

New Member

Managing a 3750

Thanks Nick, that worked a treat.  makes perfect sense now you said it.

I suppose i dont need IP routing enabled on Switch_B like i have on Switch_A, on Switch_A i use 0.0.0.0 0.0.0.0 as opposed to default-gateway command

Managing a 3750

Just a word of caution in case this doesn't work as expected.

Refer to: 

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml

The ip default-gateway command only provides the gateway to the switch as if the switch is a host device. It does not add the route to a routing table or provide support to attached devices.  This will work fine if you only need functionality to manage the switch.

Given the configuration you described, you are probably correct that you do not need routing enabled on Switch B.  Switch A will be the gateway of last resort for your VLAN 100 subnet (192.168.10.0/24).  All connected devices should use Switch A's SVI as the default gateway.  Since it has ip routing enabled and a route to an upstream next-hop (your 6500), it will route the packets appropriately.

Good luck!

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