Output of sh ip route

Answered Question
Mar 31st, 2010

Hi all,

I have 2650 router connected to Cable modem

Here is output of sh ip route

2650xm#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 96.51.144.1 to network 0.0.0.0

     64.0.0.0/32 is subnetted, 1 subnets
S       64.59.135.150 [254/0] via 96.51.144.1, FastEthernet0/0
     96.0.0.0/22 is subnetted, 1 subnets
C       96.51.144.0 is directly connected, FastEthernet0/0
C    10.0.0.0/8 is directly connected, Loopback0
C    192.168.1.0/24 is directly connected, FastEthernet1/0
S*   0.0.0.0/0 [254/0] via 96.51.144.1

I have two questions to ask

1>as i habe fa0/0 interface connected to cable modem but below thing says

C       96.51.144.0 is directly connected, FastEthernet0/0

as my router learns IP next hop 96.51.144.0 by cable modem why does it says it is directly connected even though physically it is not and far away from my router.

2>why does sh ip route show 64.0.0.0/32 is subnetted, 1 subnets
and what does it mean ???????

many thanks

mahesh

I have this problem too.
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Correct Answer by Jon Marshall about 4 years 2 weeks ago

Mahesh

this interface directly connects to cable modem.by physically far away i was saying that my router interface fa0/0 has ip 96.51.147.x and  it connects

to cable modem and next hop is 96..51.144.x.  so although next hop is far away physically from router it shows directly connected in the sh ip route?

Notice the subnet mask on your interface IP ie.

Internet address is 96.51.147.x/22

/22 = 255.255.252.0  which means that the network your interface belongs to is  96.51.144.0/22. And the network range is 96.51.144.1 -> 96.51.147.255

So your interface address and the cable modem are actually in the same network.

for second answer correct me if i am wrong so router  learns all routes that exists  in the internet through this subnet network 64.0.0.0 ?

No not at all. It simply means that the 2651 router has learnt of one route ie. 64.59.135.150/32 that is reachable via the next-hop of 96.54.144.1.

The route that tells your router how to get to all internet addresses is the default-route in your routing table -


S*   0.0.0.0/0 [254/0] via 96.51.144.1


Jon

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Jon Marshall Wed, 03/31/2010 - 05:46

mahesh18 wrote:


Gateway of last resort is 96.51.144.1 to network 0.0.0.0

     64.0.0.0/32 is subnetted, 1 subnets
S       64.59.135.150 [254/0] via 96.51.144.1, FastEthernet0/0
     96.0.0.0/22 is subnetted, 1 subnets
C       96.51.144.0 is directly connected, FastEthernet0/0
C    10.0.0.0/8 is directly connected, Loopback0
C    192.168.1.0/24 is directly connected, FastEthernet1/0
S*   0.0.0.0/0 [254/0] via 96.51.144.1

I have two questions to ask

1>as i habe fa0/0 interface connected to cable modem but below thing says

C       96.51.144.0 is directly connected, FastEthernet0/0

as my router learns IP next hop 96.51.144.0 by cable modem why does it says it is directly connected even though physically it is not and far away from my router.

2>why does sh ip route show 64.0.0.0/32 is subnetted, 1 subnets
and what does it mean ???????

many thanks

mahesh

Mahesh

1) What do you mean physically it is far away ?  What is in between your 2651 and the cable modem. What the routing table is telling you is that you have configured a 96.51.144.x address on your fa0/0 interface so the router sees this network as directly connected.

if you do a "sh ip int brief" on the 2651 do you see fa0/0 with an IP address of 96.51.44.x ?

2) This is simply a static route has been configured on your 2651 router -

ip route 64.59.135.150 255.255.255.255 96.51.144.1

the subnet bit in the routing table simply means the router only knows about one subnet from the major class A network 64.0.0.0/8. And the only subnet it knows about is 64.59.135.150/32

Jon

mahesh18 Wed, 03/31/2010 - 05:55

Hi Jon,

thanks for reply

for 1st question

here is info

2650xm#sh int fa0/0
FastEthernet0/0 is up, line protocol is up
  Hardware is AmdFE, address is 000f.8f6d.7e60 (bia 000f.8f6d.7e60)
  Description: WAN Connection to ISP modem
  Internet address is 96.51.147.x/22
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, 100BaseTX/FX
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters never
  Input queue: 2/75/2/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo

this interface directly connects to cable modem.by physically far away i was saying that my router interface fa0/0 has ip 96.51.147.x and  it connects

to cable modem and next hop is 96..51.144.x.  so although next hop is far away physically from router it shows directly connected in the sh ip route?

for second answer correct me if i am wrong so router  learns all routes that exists  in the internet through this subnet network 64.0.0.0 ?

Correct Answer
Jon Marshall Wed, 03/31/2010 - 06:04

Mahesh

this interface directly connects to cable modem.by physically far away i was saying that my router interface fa0/0 has ip 96.51.147.x and  it connects

to cable modem and next hop is 96..51.144.x.  so although next hop is far away physically from router it shows directly connected in the sh ip route?

Notice the subnet mask on your interface IP ie.

Internet address is 96.51.147.x/22

/22 = 255.255.252.0  which means that the network your interface belongs to is  96.51.144.0/22. And the network range is 96.51.144.1 -> 96.51.147.255

So your interface address and the cable modem are actually in the same network.

for second answer correct me if i am wrong so router  learns all routes that exists  in the internet through this subnet network 64.0.0.0 ?

No not at all. It simply means that the 2651 router has learnt of one route ie. 64.59.135.150/32 that is reachable via the next-hop of 96.54.144.1.

The route that tells your router how to get to all internet addresses is the default-route in your routing table -


S*   0.0.0.0/0 [254/0] via 96.51.144.1


Jon

mahesh18 Wed, 03/31/2010 - 06:09

Hi Jon,

Thanks again for explaining me the concepts.

Regards

mahesh

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