IS-IS P device cannot ping C device, 4 hops away

[TanmaySarkar]

This is my Topology, where my P-2, P-3 and devices after P-3 are unable to ping or traceroute CE-1 and C-1 devices.
Output is either-

*Oct 19 00:50:17.023: ICMP: dst (10.10.10.2) port unreachable sent to 10.10.40.5

OR, Other output is-

*Oct 19 00:54:16.139: ICMP: echo reply sent, src 10.10.10.1, dst 10.10.50.6, topology BASE, dscp 0 topoid 0

------------------------- So, my question is how many hops should I be able to ping if I have an IS-IS topology of all level-1, level-2, and level-1-2 in it?

Kindly reply I am unable to figure out what should I do. I wish this topology works with Summarization and Redistribution. 

[Georg Pauwen]

Hello,

hard to tell without seeing the configs. This looks like a GNS3 file, can you post the topology file ?

[TanmaySarkar]

Dear George,

I am really sorry, I got tired and deleted the topology, but my question is, do we need to write - "Redistribute Connected" every time we redistribute EIGRP to ISIS? and what if I use OSPF? Do I need to write this command in case of OSPF also?

[Jonathan Cuthbert · Accepted solution]

Redistribute connected is one way to redistribute between routing protocols. There are also route maps and full redistribution of the other routing protocol among other methods.

[TanmaySarkar]

Thank you for the Reply Sir.

[Jonathan Cuthbert]

In your topology, the strict Level-1-Only routers (C-1/C-2) will have no route to the strict L-2-Only routers (P-1, P-2, P-3). This is also dependent on how your areas are configured, too.

I am not sure what exact IP address you used, but when I mocked up your topology, I used the following.

C-1 = .1

CE-1 =.2

PE-1 = .3

P-1 = .4

P-2 = .5

P-3 = .6

PE-2 = .7

CE-2 = .8

C-2 =.9

The NET of the router is 49.0000.####.####.####.00

It is a large flat area.

From P-1

P-1#show ip route
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 10 subnets, 2 masks
i L2     10.10.10.0/24 [115/30] via 10.10.30.3, 00:14:06, GigabitEthernet0/0
i L2     10.10.20.0/24 [115/20] via 10.10.30.3, 00:14:06, GigabitEthernet0/0
C        10.10.30.0/24 is directly connected, GigabitEthernet0/0
L        10.10.30.4/32 is directly connected, GigabitEthernet0/0
C        10.10.40.0/24 is directly connected, GigabitEthernet1/0
L        10.10.40.4/32 is directly connected, GigabitEthernet1/0
i L2     10.10.50.0/24 [115/20] via 10.10.40.5, 00:13:56, GigabitEthernet1/0
i L2     10.10.60.0/24 [115/30] via 10.10.40.5, 00:13:56, GigabitEthernet1/0
i L2     10.10.70.0/24 [115/40] via 10.10.40.5, 00:13:56, GigabitEthernet1/0

From C-1

C-1#show ip route
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C        10.10.10.0/24 is directly connected, GigabitEthernet0/0
L        10.10.10.1/32 is directly connected, GigabitEthernet0/0
i L1     10.10.20.0/24 [115/20] via 10.10.10.2, 00:15:47, GigabitEthernet0/0

This can be confirmed with a traceroute from P-1 to CE-1 and P-1 to C-1.

P-1#traceroute 10.10.10.2
Type escape sequence to abort.
Tracing the route to 10.10.10.2
VRF info: (vrf in name/id, vrf out name/id)
  1 10.10.30.3 48 msec 36 msec 8 msec
  2 10.10.20.2 40 msec 20 msec 28 msec

P-1#traceroute 10.10.10.1
Type escape sequence to abort.
Tracing the route to 10.10.10.1
VRF info: (vrf in name/id, vrf out name/id)
  1 10.10.30.3 8 msec 16 msec 20 msec
  2 10.10.20.2 16 msec 36 msec 36 msec
  3  *  *  *
  4  *  *  * 
P-1#

The level-2 routers have knowledge of the level-1 topology because the L1/L2 routers are advertising the L1 routes into the L2 LSDB. 

The L1/L2 routers use the attached bit to advertise networks in different areas.  So it depends how you did your areas, too. 

Using strictly IS-IS, the C-1/C-2 routers have no knowledge on how to reach anything but their CE router and its interfaces.

You can solve this by creating a static default route on C-1/C-2 which would be common to see in deployment.  You can also redistribute (route leak) the L2 routes into L1.  Either is a valid solution.