[c-nsp] weird arp cache on 3750

[Aaron]

This seemed strange to me.  I transitioned management on this 3750 yesterday
from vlan 1 to 4000.  I simply shutdown vlan 1 and left old IP address on
vlan 1 interface.  This seems to have caused a problem later on.  Yesterday,
I was able to manage the 3750 fine over vlan 4000 svi, but last night 3750
rebooted during a power outage (I'm not so sure that the reboot had much to
do with it other than a clearing of arp caches and revealing a strange
behavior, but I'm not sure).  When I came in this morning I couldn't get
into 3750.  I found a strange arp entry pointing to the def gw 10.101.7.1
out "vlan 1 pv 4000".. What in the world is that?!  it wasn't able to get it
to work correctly until I removed the ip address off of vlan 1 (but vlan 1
svi was shutdown the whole time), then things were restored.  Anyone know
anything about this?

 

3750#sh ip arp vl 1

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.1              1   c062.6bb0.7fad  ARPA   Vlan1 pv 4000

 

3750#sh ip arp vl 4000

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.8              -   e840.40ce.65c1  ARPA   Vlan4000

Internet  10.101.7.10             0   34db.fd1a.a840  ARPA   Vlan4000

 

3750#cle arp int vl 1

 

3750#cle arp int vlan 4000

 

3750#sh ip arp vl 4000

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.8              -   e840.40ce.65c1  ARPA   Vlan4000

Internet  10.101.7.10             0   34db.fd1a.a840  ARPA   Vlan4000

 

3750#sh ip arp vl 1

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.1              0   c062.6bb0.7fad  ARPA   Vlan1 pv 4000

 

3750#clear arp interface vl 1

 

3750#sh ip arp vl 1

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.1              0   c062.6bb0.7fad  ARPA   Vlan1 pv 4000

 

3750#sh ip arp vl 1

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.1              0   c062.6bb0.7fad  ARPA   Vlan1 pv 4000

 

3750#clear arp interface vlan 1

3750#clear arp interface vlan 1

3750#clear arp interface vlan 1

3750#clear arp interface vlan 1

3750#clear arp interface vlan 1

 

**** IT WOULDN'T CLEAR ****

 

 

3750#sh ip arp vl 1

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.1              0   c062.6bb0.7fad  ARPA   Vlan1 pv 4000

 

3750#ib vl 1

Interface              IP-Address      OK? Method Status
Protocol

Vlan1                  192.168.200.73  YES NVRAM  administratively down down

 

3750#sh run in vl 1

Building configuration...

Current configuration : 74 bytes

!

interface Vlan1

ip address 192.168.200.73 255.255.255.0

shutdown

end

3750#conf t

Enter configuration commands, one per line.  End with CNTL/Z.

3750(config)#int vl 1

3750(config-if)#no ip address

 

**** RIGHT THEN PINGS CAME BACK FOR THIS 3750, apparently having that old ip
address still on vlan 1 was breaking things ****

3750(config-if)#^Z

3750#sh run in vl 1

Building configuration...

Current configuration : 48 bytes

!

interface Vlan1

no ip address

shutdown

end

3750#sh ip arp vl 1

3750#sh ip arp vl 4000

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.101.7.8              -   e840.40ce.65c1  ARPA   Vlan4000

Internet  10.101.7.10             1   34db.fd1a.a840  ARPA   Vlan4000

Internet  10.101.7.1              0   c062.6bb0.7fad  ARPA   Vlan4000

 

3750#wr

Building configuration...

[OK]

 

Model number                    : WS-C3750G-24TS-S1U

Cisco IOS Software, C3750 Software (C3750-IPBASE-M), Version 12.2(50)SE5,
RELEASE SOFTWARE (fc1)

 

Aaron