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A WAN link is always going down then comes back up after diagnostics like ping

Agustin Jr Matib

On of my WAN link is always going down. When I run diagnostics (ping gateway or 8.8.8.8) it would come back up but after 3 to 5 hours it would go down again. I have another WAN interface with the same ISP, same configuration only differs in IP address but does not have any issues like the one I described.

I suspected the interface link of the switch and the sophos appliance because I have changed the Sophos interface speed and was receiving errors. I have configured auto-nego on both on the switch and sophos then did no longer see any errors but the problem I described earlier is still present. What puzzles me is that I have a WAN interface with the same switch and same ISP that is doing fine.



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  • 0

    Hi  

    Hope your another WAN from same ISP provider not falling in the same network subnet as it is not recommended to configure 2 same network on 2 different Interface of XG and this may create such problem due to ARP conflict. If this is not the case and you have already 2 different network on both the WAN link from your ISP provider then you may confirm below output and details when your WAN link going down.

    You may check the gateway IP ARP on XG for down gateway, If ARP is fine then check TCPDUMP during PING to gateway IP and external public IP.

    How to check ARP :

    console> sy dia ut arp show 10.201.208.254

    It should give ARP output via above command to next device physical address. If ARP is present then do the PING to gateway IP and confirm the tcpdump. Also at the same time do the PING to any external IP like 8.8.8.8, 4.2.2.2 via that ISP and confirm the TCPDUMP.

    PING via specific Interface:

    console> ping interface Port2 8.8.8.8
    PING 8.8.8.8 (8.8.8.8): 56 data bytes
    64 bytes from 8.8.8.8: seq=0 ttl=113 time=11.693 ms
    64 bytes from 8.8.8.8: seq=1 ttl=113 time=11.421 ms

    TCPDUMP command for ICMP tracking on specific host on which you generated PING:

    console>tcpdump 'host 8.8.8.8 and proto ICMP

Reply
  • 0

    Hi  

    Hope your another WAN from same ISP provider not falling in the same network subnet as it is not recommended to configure 2 same network on 2 different Interface of XG and this may create such problem due to ARP conflict. If this is not the case and you have already 2 different network on both the WAN link from your ISP provider then you may confirm below output and details when your WAN link going down.

    You may check the gateway IP ARP on XG for down gateway, If ARP is fine then check TCPDUMP during PING to gateway IP and external public IP.

    How to check ARP :

    console> sy dia ut arp show 10.201.208.254

    It should give ARP output via above command to next device physical address. If ARP is present then do the PING to gateway IP and confirm the tcpdump. Also at the same time do the PING to any external IP like 8.8.8.8, 4.2.2.2 via that ISP and confirm the TCPDUMP.

    PING via specific Interface:

    console> ping interface Port2 8.8.8.8
    PING 8.8.8.8 (8.8.8.8): 56 data bytes
    64 bytes from 8.8.8.8: seq=0 ttl=113 time=11.693 ms
    64 bytes from 8.8.8.8: seq=1 ttl=113 time=11.421 ms

    TCPDUMP command for ICMP tracking on specific host on which you generated PING:

    console>tcpdump 'host 8.8.8.8 and proto ICMP

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  • 0 in reply to Vishal_R

    Hi, Thank you sir for finding time to reply.

    Well, it does fall under the same subnet. PortA2 is XXX.XXX.156.244/27 then I Also have Aliases configured under the same interface for port forwarding into my webservers. Works fine, no problem. Then I configured PortA7 (I also tried it in PortA1) interface for IP addess XXX.XXX.156.241/27. It will only work for 3-4 hours then it will report as down then I will have to ping from interface PortA7 for the gateway to come back up and the cycle goes on. I tried checking the interface MAC address and they have different MAC.

    If "it is not recommended to configure 2 same network on 2 different Interface of XG and this may create such problem due to ARP conflict." What could be other solution so that when our webservers will access the internet they will use PortA2 (or another interface)  but when users will access internet they will use PortA7 or another interface using the same ISP or gateway? I need them to be using different interface so that I could to monitor their traffic in the sophos interfaces or in the switch interfaces.

  • +1 in reply to Agustin Jr Matib

    Hi  

    Other solution would be to ask ISP to provide another network ( different from PortA2) to configure on PortA7 or configure PortA7 network to any other router and from that router LAN or DHCP assign PortA7 private network. 

  • 0 in reply to Vishal_R

    Thank You, We'll have to put up other private address for that purpose.