ARP is sourced from loopback address

Joe Maimon jmaimon at ttec.com
Mon Jan 30 15:27:50 CST 2012


Hey All,

Anycast related.

Is this normal behavior? Whats the workaround? Why havent I run into 
this before?

192.168.76.1 is a HSRP address on a ring of routers transiting a private 
non routed vlan to the service addresses hosted on systems that have 
independent management interfaces.

Best,

Joe


root at debian31:~# ifconfig lo:0
lo:0      Link encap:Local Loopback
           inet addr:209.54.140.64  Mask:255.255.255.255
           UP LOOPBACK RUNNING  MTU:16436  Metric:1

root at debian31:~# ip rule list
0:      from all lookup local
32764:  from 209.54.140.0/24 lookup pbr1-exit
32765:  from 216.222.144.16/28 lookup pbr1-exit
32766:  from all lookup main
32767:  from all lookup default
root at debian31:~# ip route list table pbr1-exit
default via 192.168.76.1 dev eth1
192.168.34.0/24 dev eth1  scope link  src 192.168.76.16
192.168.76.0/24 dev eth1  scope link  src 192.168.76.16
root at debian31:~# tcpdump -i eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes

11:08:09.053943 ARP, Request who-has 192.168.76.1 tell 209.54.140.64, 
length 28
11:08:10.035126 IP noc08rt08.noc08.chl.net > 209.54.140.64: ICMP echo 
request, id 517, seq 0, length 80
11:08:10.051276 ARP, Request who-has 192.168.76.1 tell 209.54.140.64, 
length 28
11:08:11.052548 ARP, Request who-has 192.168.76.1 tell 209.54.140.64, 
length 28
11:08:12.035964 IP noc08rt08.noc08.chl.net > 209.54.140.64: ICMP echo 
request, id 517, seq 1, length 80
^C

root at debian31:~# ip neigh
fe80::230:71ff:fe3b:6808 dev eth0 lladdr 00:30:71:3b:68:08 router STALE
192.168.76.1 dev eth1  FAILED
192.168.34.254 dev eth0 lladdr 00:11:93:04:7a:1b DELAY
192.168.34.48 dev eth0 lladdr 00:0c:29:fd:64:8a STALE

root at debian31:~# uname -a
Linux debian31 3.2.0-1-686-pae #1 SMP Tue Jan 24 06:09:30 UTC 2012 i686 
GNU/Linux

root at debian31:~# ping 192.168.76.1
PING 192.168.76.1 (192.168.76.1) 56(84) bytes of data.
64 bytes from 192.168.76.1: icmp_req=1 ttl=255 time=2.95 ms
^C
--- 192.168.76.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 2.952/2.952/2.952/0.000 ms
root at debian31:~# ip neigh
fe80::230:71ff:fe3b:6808 dev eth0 lladdr 00:30:71:3b:68:08 router STALE
192.168.76.1 dev eth1 lladdr 00:00:0c:9f:f0:01 REACHABLE
192.168.34.254 dev eth0 lladdr 00:11:93:04:7a:1b REACHABLE
192.168.34.48 dev eth0 lladdr 00:0c:29:fd:64:8a STALE
192.168.76.2 dev eth1 lladdr 00:b0:4a:9e:54:00 STALE
root at debian31:~# !tcp
tcpdump -i eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
11:12:22.476479 IP noc08rt08-l0.noc08.chl.net > 209.54.140.64: ICMP echo 
request, id 518, seq 0, length 80
11:12:22.476572 IP 209.54.140.64 > noc08rt08-l0.noc08.chl.net: ICMP echo 
reply, id 518, seq 0, length 80
11:12:22.479495 IP noc08rt08-l0.noc08.chl.net > 209.54.140.64: ICMP echo 
request, id 518, seq 1, length 80
11:12:22.479533 IP 209.54.140.64 > noc08rt08-l0.noc08.chl.net: ICMP echo 
reply, id 518, seq 1, length 80
11:12:22.484346 IP noc08rt08-l0.noc08.chl.net > 209.54.140.64: ICMP echo 
request, id 518, seq 2, length 80
11:12:22.484392 IP 209.54.140.64 > noc08rt08-l0.noc08.chl.net: ICMP echo 
reply, id 518, seq 2, length 80
11:12:22.487670 IP noc08rt08-l0.noc08.chl.net > 209.54.140.64: ICMP echo 
request, id 518, seq 3, length 80
11:12:22.487705 IP 209.54.140.64 > noc08rt08-l0.noc08.chl.net: ICMP echo 
reply, id 518, seq 3, length 80
11:12:22.490639 IP noc08rt08-l0.noc08.chl.net > 209.54.140.64: ICMP echo 
request, id 518, seq 4, length 80
11:12:22.490675 IP 209.54.140.64 > noc08rt08-l0.noc08.chl.net: ICMP echo 
reply, id 518, seq 4, length 80
^C





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