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Cisco Employee

latency observed on ping'ing loopback ip

Hi team,

We have 2 3945/15.0(1)M7 connected via gig interface to upstream routers (4 routers running MPLS BGP in core, dedicated for IP SLA probes) and we can ping physical interface IP just fine no delay but when ping loopback interface ping response time latency varies any where from 1 ms to 22 ms and we are looking for ways to find out if something in control plane of 3900 is causing this delay, any help is much appreciated.

Topology and config is like this

FRFRPARP301NSR01:

sho ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0         unassigned      YES NVRAM  administratively down down    
GigabitEthernet0/1         10.251.63.117   YES NVRAM  up                    up      
GigabitEthernet0/2         10.251.63.9     YES NVRAM  up                    up      
Loopback0                  10.250.230.207  YES manual up                    up      
Loopback1                  10.250.230.206  YES manual up                    up      
Loopback2                  10.250.230.205  YES manual up                    up      
Loopback3                  10.250.230.204  YES manual up                    up 

nterface Loopback0
 description Router Integrity Enterprise Template rollout for BOA AUDIT Feb 2005
 ip address 10.250.230.207 255.255.255.255
!
interface Loopback1
 description Tier 1 poller source
 ip address 10.250.230.206 255.255.255.255
!
interface Loopback2
 description Tier 2 poller source
 ip address 10.250.230.205 255.255.255.255
!
interface Loopback3
 description Reserved
 ip address 10.250.230.204 255.255.255.255


interface GigabitEthernet0/2
 description FRFRPARP301GER01B_GE0/0/1/1
 mtu 9000
 ip address 10.251.63.9 255.255.255.254
 no ip redirects
 no ip proxy-arp
 duplex full
 speed auto

GigabitEthernet0/2 is up, line protocol is up 
  Hardware is PQ3_TSEC, address is c464.1326.b982 (bia c464.1326.b982)
  Description: FRFRPARP301GER01B_GE0/0/1/1
  Internet address is 10.251.63.9/31
  MTU 9000 bytes, BW 1000000 Kbit/sec, DLY 10 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is SX
  output flow-control is XON, input flow-control is XON
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 04:53:18
  Input queue: 1/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 257000 bits/sec, 165 packets/sec
  5 minute output rate 255000 bits/sec, 163 packets/sec
     3170656 packets input, 604643921 bytes, 0 no buffer
     Received 448 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 448 multicast, 0 pause input
     0 input packets with dribble condition detected
     3173300 packets output, 605343966 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out

FRFRPARP301NSR01#ping 10.250.230.223
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.223, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
FRFRPARP301NSR01#ping 10.250.230.222
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.222, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/22/24 ms
FRFRPARP301NSR01#ping 10.250.230.223
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.223, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms
FRFRPARP301NSR01#ping 10.250.230.221
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.221, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/12/12 ms
FRFRPARP301NSR01#ping 10.250.230.220
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.220, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/12/12 ms
FRFRPARP301NSR01#

2nd NSR rtr:
FRFRPART301NSR01#sho ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0         unassigned      YES manual administratively down down    
GigabitEthernet0/1         10.251.63.245   YES NVRAM  up                    up      
GigabitEthernet0/2         10.251.63.137   YES manual up                    up      
Loopback0                  10.250.230.223  YES manual up                    up      
Loopback1                  10.250.230.222  YES manual up                    up      
Loopback2                  10.250.230.221  YES manual up                    up      
Loopback3                  10.250.230.220  YES manual up                    up      

(I'm pinging the 1st NSR's loopbacks way above)
FRFRPART301NSR01#ping 10.250.230.207
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.207, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/22/24 ms
FRFRPART301NSR01#ping 10.250.230.206
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.206, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
FRFRPART301NSR01#ping 10.250.230.205
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.205, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/12/12 ms
FRFRPART301NSR01#ping 10.250.230.204
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.250.230.204, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/12/12 ms
FRFRPART301NSR1#

- no interface errors

- cpu is less than 5%

- no controller level errors

Please let me know if any information is required from devices.

thanks

Manish

Everyone's tags (3)
1 REPLY

latency observed on ping'ing loopback ip

Hi Manish,

I guess there should be some rate limiting in the RIB/CP for ICMP packet for loopback. Because when you say ping the loop back and if you enable the debug for icmp packets and routing... This will say src and dest as the same ip which is routed via the RIB.

By

Karthik

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