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I'm using a web application known as IOU-Web. This application is used to execute CISCO IOS software in a browser. Here is what topology looks like

And here is what interfaces config snap

Now the idea is that R1 should be able to access the host machine which is my Laptop (Ubuntu-12.04). When I ping from my laptop terminal to R1, R1 successfully caches the ARP entry against my laptop Eth1 MAC. However, Ubuntu does not cache / update the MAC address of R1. I used tcpdump to inspect the traffic and interestingly, I can see the ARP reply from R1. Then I also tried static binding of R1-MAC in the Ubuntu ARP table, but even after that I was unable to ping R1. Though a debug on R1 shows that it did send reply to echo requests (ping).

TL;DR My Ubuntu machine is not updating its ARP-cache even though ARP replies are being recived.

Earlier I had done some googling and stumbled upon a post where it mentioned a similar issue being resolved by disabling "Reverse Path Forwarding Kernel Parameter". That kinda made sense and I tried that solution as well by disabling "RP_Filter" using the command

sudo sh -c 'echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter'

and

sudo sh -c 'echo 0 > /proc/sys/net/ipv4/conf/eth1/rp_filter'

But that didn't help either. Can someone please give some tips on possible course of action to resolve this issue?

Zanna
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Ahmad Nadeem
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  • @Zanna, didn't know that English grammar is checked as well. Thanks for the editing though :) – Ahmad Nadeem Dec 20 '16 at 08:18
  • hmm hope you didn't find it aggressive. Grammar isn't a big deal (especially when, as in this case, the post is perfectly understandable already), but I wanted to fix those links especially. I'm a bit of a compulsive editor! – Zanna Dec 20 '16 at 08:27
  • @Zanna, Aggressive? Not at all, Infact I'm glad that you made it more comprehensive and converted links to images. And as always I'm so grateful for the time and work that you guys spend over here to make these forums helpful, informational and clean. – Ahmad Nadeem Dec 20 '16 at 08:37
  • :) we do what we can. Thanks for the kind words. I will come back and clean up my comments when I remember to – Zanna Dec 20 '16 at 08:43
  • How do you know your ubuntu machine isn't updating the arp cache? What is the output of `arp -a` immediately after pinging ubuntu VM from R1? – user4556274 Dec 20 '16 at 12:57
  • :) I know because arp -an shows the entry against R1 as incomplete. – Ahmad Nadeem Dec 20 '16 at 15:17

0 Answers0