We have a lot of Cisco 3020 (WS-CBS3020-HPQ) but one pair in an HP enclosure have been providing very strange ARP entries.
The blade module has 1 port channel down stream to a 4948 and is connected to serveral blades servers upstream. Management is provided by a Fastethernet0 port which sees the other blade module and our iLO switch. We have one vlan (Vlan 100) configured and initially the fast0 port was getting it's ip address via DHCP configured from the enclosure. This problem started about a week ago and so we have now assigned the address statically and the default gateway for fast0 to see if this would resolve the issue.
The Fast0 address is 10.60.67.49/22 and default gateway is 10.60.64.1. We are now no longer able to directly connect to the 3020 and it's adding strange entries into the arp table.
In a normal 3020 we see a table as follows:
Internet 10.60.64.2 27 0024.f71d.dac1 ARPA FastEthernet0
Internet 10.60.64.3 15 0024.f719.cdc1 ARPA FastEthernet0
Internet 10.60.64.1 72 0000.0c9f.f096 ARPA FastEthernet0 -- HSRP address
In the faulty 3020 we see:
Internet 10.60.64.2 18 0024.f71d.dac1 ARPA FastEthernet0
Internet 10.60.64.3 0 0024.f719.cdc1 ARPA FastEthernet0
Internet 10.60.64.1 10 001b.531b.2a41 ARPA Vlan100
The Vlan 100 is in address range 10.60.1.0/24
How is is possible that the default gateway arp entry is being learned via vlan 100 which is in a completly different ip address range?