02-05-2013 09:10 AM - edited 03-04-2019 06:56 PM
I have a Cisco 2801 with dual ADSL WAN connections, PATing to a network hanging on the fa0/1 interface. From the server connected to the router (hanging off of the fa0/1) interface, I can ping any address and there are no issues. But from inside the Cisco CLI, pinging certain addresses causes erratic behavior. Here are the results when I try to ping:
Sending 5, 1492-byte ICMP Echos to 4.2.2.2, timeout is 2 seconds:
Packet sent with the DF bit set
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/83/116 ms
Sending 5, 1465-byte ICMP Echos to 4.2.2.2, timeout is 2 seconds:
Packet sent with the DF bit set
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/183/380 ms
Type escape sequence to abort.
Sending 5, 1473-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
!!..!
Success rate is 60 percent (3/5), round-trip min/avg/max = 220/252/300 ms
BrightAngel#ping 8.8.8.8 size 1473 df-bit
Type escape sequence to abort.
Sending 5, 1473-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
Packet sent with the DF bit set
....!
Success rate is 20 percent (1/5), round-trip min/avg/max = 88/88/88 ms
BrightAngel#ping 8.8.8.8 size 1473 df-bit
Type escape sequence to abort.
Sending 5, 1473-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
Packet sent with the DF bit set
...!!
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
!..!.
Success rate is 40 percent (2/5), round-trip min/avg/max = 592/634/676 ms
One other interesting issue is that from the WANside of the router, I can successfully ping with packets of any MTU size except for the range 1465-1472.
Here are the Dialers configs:
interface Dialer1
ip address negotiated
no ip proxy-arp
ip mtu 1492
ip nat outside
ip virtual-reassembly
encapsulation ppp
ip tcp adjust-mss 1452
dialer pool 1
no cdp enable
interface Dialer2
ip address negotiated
no ip proxy-arp
ip mtu 1492
ip nat outside
ip virtual-reassembly
encapsulation ppp
ip tcp adjust-mss 1452
dialer pool 2
no cdp enable
02-20-2013 03:58 PM
This purely depends on Farend where the IP is hosted. There are ping rate limits applied by google, due to this you are facing issue.
Just check only, if you are facing any service degradation because of this. We can't conclude by just ping for these google IPs
02-25-2013 09:55 AM
Well to be fair, I never have an issue pinging 8.8.8.8 from any other functioning interface. Also i didn't show it, but if I ping google with the LAN interface as the source address, I get a 100% success rate reply. However I did describe the that the server hanging off of the LAN interface gets a 100% success rate when pinging google.
02-20-2013 06:52 PM
Dialers:
Ip mtu 1472
Alessio
Sent from Cisco Technical Support iPad App
02-25-2013 09:23 AM
Thanks for the suggestion. That might be a good choice for a PPPoE encapsulation, but this particular encapsulation is a PPPoA. Sorry I forgot to include the #sh run int ATM.
02-25-2013 12:44 PM
update:
The problem may well have been caused by one of the DSL lines. The line went down suddenly. I rebooted the router after a day or 2, and the connection was made immediately. Now I get different results: 100% success rates from any interface and speedier ping times. Here is what it looks like now:
(But there is something odd happening; notice how the last traceroute goes out both dialer interfaces! Is that supposed to happen?)
Cisco2801#ping 8.8.8.8
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 84/85/88 ms
Cisco2801#ping 4.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 4.2.2.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 48/58/68 ms
Cisco2801#traceroute 8.8.8.8
Type escape sequence to abort.
Tracing the route to 8.8.8.8
1 *
67.X.X.214 48 msec 48 msec
2 75.160.237.121 52 msec 32 msec *
3 *
67.14.22.182 64 msec 60 msec
4 63.156.131.190 44 msec 100 msec *
5 209.85.248.185 40 msec 60 msec *
6 *
72.14.238.2 84 msec
72.14.238.0 100 msec
7 *
72.14.239.155 96 msec
72.14.239.153 100 msec
8 216.239.48.165 80 msec
216.239.48.167 84 msec *
9 * * *
10 *
8.8.8.8 84 msec 96 msec
Cisco2801#traceroute 8.8.8.8
Type escape sequence to abort.
Tracing the route to 8.8.8.8
1 * *
67.X.X.240 36 msec
2 75.160.237.121 36 msec *
216.160.199.169 48 msec
3 67.14.22.182 60 msec 68 msec *
4 63.156.131.190 60 msec 60 msec 60 msec
5 * *
209.85.248.187 40 msec
6 72.14.238.0 96 msec * 100 msec
7 72.14.239.160 96 msec
72.14.239.162 80 msec 84 msec
8 216.239.48.167 100 msec 96 msec
64.233.174.131 84 msec
9 * * *
10 8.8.8.8 96 msec * *
Cisco2801#traceroute 4.2.2.2
Type escape sequence to abort.
Tracing the route to 4.2.2.2
1 * *
67.X.X.240 32 msec
2 75.160.237.121 36 msec * *
3 67.14.22.78 40 msec 44 msec *
4 63.146.27.34 60 msec 60 msec 44 msec
5 4.69.144.201 44 msec * *
6 4.2.2.2 40 msec * 60 msec
Cisco2801#traceroute 8.8.8.8
Type escape sequence to abort.
Tracing the route to 8.8.8.8
1 67.X.X.214 48 msec
67.X.X.240 32 msec 36 msec
2 *
216.160.199.169 48 msec 48 msec
3 67.14.22.182 52 msec * 44 msec
4 63.156.131.190 60 msec * *
5 209.85.248.187 60 msec 60 msec 48 msec
6 *
72.14.238.0 84 msec
64.233.174.190 60 msec
7 * *
72.14.239.162 96 msec
8 64.233.174.131 100 msec
216.239.48.167 84 msec *
9 * * *
10 8.8.8.8 96 msec 80 msec 80 msec
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