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Community Member

Need help in intrepreting the results in sh ip route and traceroute

Hi,

Can you explain the sh route in red? What path would it take to get to 10.245.65.4/30? I did a traceroute and am still confused.

TIA.

PF

sh 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 172.31.19.1 to network 0.0.0.0

     172.31.0.0/16 is variably subnetted, 9 subnets, 2 masks
C       172.31.34.0/28 is directly connected, Vlan734
C       172.31.33.0/28 is directly connected, Loopback0
C       172.31.32.0/28 is directly connected, Vlan732
C       172.31.19.0/28 is directly connected, Vlan719
R       172.31.18.0/24 [120/1] via 172.31.19.1, 00:00:26, Vlan719
R       172.31.17.0/28 [120/1] via 172.31.19.1, 00:00:26, Vlan719
R       172.31.2.0/28 [120/2] via 172.31.19.1, 00:00:26, Vlan719
R       172.31.1.0/24 [120/2] via 172.31.19.1, 00:00:26, Vlan719
R       172.31.4.0/28 [120/1] via 172.31.19.1, 00:00:26, Vlan719
R    203.18.122.0/24 [120/5] via 172.31.34.2, 00:00:25, Vlan734
     10.0.0.0/8 is variably subnetted, 18 subnets, 5 masks
R       10.10.24.0/23 [120/2] via 172.31.19.1, 00:00:26, Vlan719
R       10.10.26.0/25 [120/1] via 172.31.19.1, 00:00:26, Vlan719
R       10.10.27.0/25 [120/2] via 172.31.19.1, 00:00:26, Vlan719
R       10.10.28.0/24 [120/1] via 172.31.19.1, 00:00:26, Vlan719
R       10.10.29.0/25 [120/3] via 172.31.34.2, 00:00:25, Vlan734
C       10.10.30.0/23 is directly connected, Vlan30
R       10.245.64.252/30 [120/5] via 172.31.34.2, 00:00:25, Vlan734
R       10.245.64.40/29 [120/2] via 172.31.34.2, 00:00:25, Vlan734
R       10.10.26.128/25 [120/1] via 172.31.19.1, 00:00:26, Vlan719
R       10.10.27.128/25 [120/2] via 172.31.19.1, 00:00:26, Vlan719
R       10.245.65.28/30 [120/1] via 172.31.34.2, 00:00:25, Vlan734
R       10.245.65.24/30 [120/5] via 172.31.19.1, 00:00:26, Vlan719
R       10.245.64.24/29 [120/1] via 172.31.34.2, 00:00:25, Vlan734
R       10.245.65.20/30 [120/3] via 172.31.34.2, 00:00:25, Vlan734
R       10.245.65.16/30 [120/3] via 172.31.34.2, 00:00:25, Vlan734
R      10.245.65.4/30 [120/3] via 172.31.34.2, 00:00:25, Vlan734
                       [120/3] via 172.31.19.1, 00:00:26, Vlan719

R       10.245.65.0/30 [120/3] via 172.31.34.2, 00:00:25, Vlan734
R       10.245.64.0/29 [120/2] via 172.31.34.2, 00:00:25, Vlan734
R*   0.0.0.0/0 [120/2] via 172.31.19.1, 00:00:26, Vlan719
R    203.18.112.0/21 [120/5] via 172.31.34.2, 00:00:25, Vlan734

traceroute
Protocol [ip]:
Target IP address: 10.245.65.5
Source address: 10.10.30.1
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 10.245.65.5

  1 172.31.19.1 0 msec
    172.31.34.2 0 msec
    172.31.19.1 8 msec
  2 10.245.64.25 0 msec
    172.31.4.1 0 msec
    10.245.64.25 8 msec
  3 10.10.24.1 0 msec
    10.245.64.1 0 msec *

4 REPLIES
Cisco Employee

Re: Need help in intrepreting the results in sh ip route and tra

Hello,

The routes

R      10.245.65.4/30 [120/3] via 172.31.34.2, 00:00:25, Vlan734
                       [120/3] via 172.31.19.1, 00:00:26, Vlan719

indicate that the RIP routing protocol is learning it via two different paths and both have equal costs. Cisco Routers support upto 4 route installations (with equal cost). If you have disabled fast switching, then the router will do per-packet loadbalancing. In this case, since the traffic is ICMP, it is automatically sent to CPU and the CPU will do loadbalancing automatically based on the routing table.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094820.shtml

Hope this helps.

Regards,

NT

Community Member

Re: Need help in intrepreting the results in sh ip route and tra

Nagaraja,

Thanks for the reply.  If I don't want load balancing to occur, how do I ensure that it uses this path via 172.31.19.1 for instance?

Thanks.

PF

Cisco Employee

Re: Need help in intrepreting the results in sh ip route and tra

Hello,

You can use offset list under the RIP for that specific subnet.

access-list 1 permit 10.245.65.4 0.0.0.3

access-list 1 deny any

router rip

offset-list 1 in 3 vlan 734

exit

This will add 3 to the hop count learnt on VLAN 734 and the router will

install only the lower cost route i.e. through 172.31.19.1 (VLAN 719).

Hope this helps.

Regards,

NT

Community Member

Re: Need help in intrepreting the results in sh ip route and tra

Nagaraja,

Thanks very much.

PF

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