Issues about EIGRP between two core switches

[cole xu]

Hello

Please find the part of basic information about my current network design from below:

1. Test-core-01

    Vlan 110: 192.168.110.2/24

    Vlan 901: 192.168.90.2/24

2. Test-core-02

    Vlan 110: 192.168.110.3/24

    Vlan 901: 192.168.90.3/24

Diagram:

I'm doing a test in order to reach the following targets:

1.  Pc1 get ip address from dhcp server(192.168.110.2)    -   Successfully

2.  Pc2 get ip address from dhcp server(192.168.110.2)    -   Failed

3.  Test via ping command       

     ping 192.168.110.3 from Test-core-01                        -    Failed

     ping 192.168.110.2 form Test-core-02                        -    Successfully

Need your kindly help to check the config and expect your advice on what to do . thanks!

[jonathanaxford · Accepted solution]

Hi,

It looks to me like you may be causing some routing issues by having the VLAN110 subnet exist on both sides of the routed link between the core switches.

The "Core-1" switch that houses the DHCP server will correctly being able to get a DHCP address. The "Core-2" switch will not be able to access the DHCP server as it will think that the device is located on a directly connected interface (Interface VLAN 110).

This is the same reason that the PING tests will be failing to the devices off of Core-2. When you attempt to PING 192.168.110.3 from Core-1, the device will look in its routing table and see that the 192.168.110.0/24 network is directly connected via Interface VLAN 110. So, it will attempt to forward the frame via VLAN 110 - any access ports configured in that VLAN will receive the traffic, but it will not be forwarded over the VLAN 901 link to the other switch.

If you created new VLANs on Core-2 on a different IP subnet, you would fine that things will start to work properly.

Hope this helps a little,

Many thanks

Jonathan

[cole xu]

Hi,

Thanks a lot for your help . I created a new vlan(vlan 120) on core-02 and it's working now. If I also wanna vlan 110 can work successfully, is it possible to add the following commands on both core switch?

standby 110 priority xxx
standby 110 preempt

I'll reply you when the test is done. thanks!