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Community Member

Some switches unreachable

Hi,

I have a strange situation. I have 15 pcs of C2960S, all of them connected to a 4500-X by 10 Gb fiber. All the switches are in VLAN 9 - the have 192.168.1.x/24 IP addresses. In VLAN 1 - 172.16.5.0/24 I have CPI v 1.3

6 switches are not reachable by CPI, and indeed, I can't ping CPI from those switches and viceversa.

The configs for all 15 switches are identical.

What I noticed wierd on non-reacheble switches is the arp table. I put a paste from both working an non-working swithes. (172.16.5.75 -is the CPI server)

1. Working:

Switch8#sh arp

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  192.168.1.10            -   f029.29bc.8f41  ARPA   Vlan9

Internet  192.168.1.1             0   4c4e.3597.4cbf  ARPA   Vlan9

Internet  172.16.5.75            91   4c4e.3597.4cbf  ARPA   Vlan9

2. Non working:

Switch7#sh arp

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  172.16.5.75             5   000c.298c.fb42  ARPA   Vlan1

Internet  192.168.1.1             0   4c4e.3597.4cbf  ARPA   Vlan9

Internet  192.168.1.9             -   f029.2983.95c1  ARPA   Vlan9

I don't know why in the non-working switch the host appears in VLAN1.

Please help!

Thanks a lot!

Adrian

3 REPLIES
Community Member

Some switches unreachable

could you please confirm whether all the interconnecting switch ports are configures as trunk

Community Member

Re: Some switches unreachable

Yes, of course.

The TenGigas are "switchport mode trunk" and the others are:

"switchport access vlan x

switchport mode access"

In the meantime I noticed something: if I do clear arp, ping 172.16.5.75 twice it starts functioning, and the arp looks like:

Switch11#sh arp

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  192.168.1.1             0   4c4e.3597.4cbf  ARPA   Vlan9

Internet  192.168.1.13            -   8875.56b9.5841  ARPA   Vlan9

which looks good, but not lasts forever, after a while stops working.

Community Member

Re: Some switches unreachable

Hello Adrian,

It looks like the ARP entry for the 172.16.5.75 or the Mac Addres on the port are aging out, that's why you see it working and "after some time it stops working".

By the time that you experience the issue, check the "show mac-address interface " and check the "show arp" where the server is connected.

You can fix this issue (temporarily) by putting the ARP entry for this IP address

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