Sigh, rookie mistake. The command arp timeout
is available in interface configuration mode only, and is set specific to each interface. You can view the setting in show interface
:
router1# conf t
Enter configuration commands, one per line. End with CNTL/Z.
router1(config)# arp timeout 99999
^
% Invalid input detected at '^' marker.
router1(config)# int eth0/1
router1(config-if)# arp timeout 99999
router1(config-if)# end
*Jan 11 17:37:56.285: %SYS-5-CONFIG_I: Configured from console by console
router1# show int eth0/1 | i Timeout
ARP type: ARPA, ARP Timeout 1d03h
router1# show int eth0/1
Ethernet0/1 is administratively down, line protocol is down
Hardware is AmdP2, address is aabb.cc00.0110 (bia aabb.cc00.0110)
MTU 1500 bytes, BW 10000 Kbit/sec, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
ARP type: ARPA, ARP Timeout 1d03h
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
...