Hello Ayong
There may be several areas in which the routing is failing for your communication from a non-ISIS router to an ISIS router. To determine where the problem is, I suggest you try some of the following:
- Try a “mirror image” of the ping that worked. In other words, if ISIS_R1 pinged EIGRP_R1 successfully, try to ping the exact opposite. Make sure however that you are using the same source and distination IPs!! If you just use ping, the router may choose a different source IP. More info about ping can be found at this lesson. I have a hunch that if you do this, your ping will work.
- If it doesn’t, then trace the proper path that such a packet should take, and write down the expected next-hop IPs for each of the routers it passes through. Check the routing table of each of those routers and see that the routers do indeed have a next-hop router configured for that destination, or if a default gateway is serving your destination correctly. Remember to trace both directions! It could be that the ping successfully reaches the destination, but the return trip fails! By doing this, you will find the specific router which drops the packet. You can then investigate why that router doesn’ thave a proper route to serve that destination.
Once you perform these steps, you should be in a position to determine the reason for the failure, whether it is redistribution or not. The fact that your initial pings worked tell me that redistribution is working correctly, at least for the source and destination IP addresses in question.
Try this out and let us know how you get along…
I hope this has been helpful!
Laz