I haven't tried this on my other routers, but is there a possibility that this command doesn't work on the 2610xm running 12.4 IOS?
2610xm#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
10.0.0.0/24 is subnetted, 3 subnets
C 10.1.1.0 is directly connected, FastEthernet0/0
C 10.1.130.0 is directly connected, Serial1/0
C 10.1.128.0 is directly connected, Serial1/3
2610xm#ter
2610xm#terminal ip
2610xm#terminal ip ?
netmask-format Change display of netmasks
tcp TCP options
2610xm#terminal ip netmask-format decimal
2610xm#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
10.0.0.0/24 is subnetted, 3 subnets
C 10.1.1.0 is directly connected, FastEthernet0/0
C 10.1.130.0 is directly connected, Serial1/0
C 10.1.128.0 is directly connected, Serial1/3
2610xm#