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Router latency

Asked by didier_09 in Network Routers, Frame Relay, Network Switches & Hubs

Tags: Cisco 1721

I have been noticing a difference in latency for a point-to-point connection.  The point-to-point is a full T1 with Cisco 1721 routers on both ends.  The line is used for both voice and data, with voice having priority.  

In the past, when I would ping from point A to point B or from point B to point A, the round trip time would be a solid 4ms.  Recently, when I ping from point A to point B it shows a 1ms round trip time, but pinging from point B to point A remains 4ms.  These are the latency times when I ping from workstations behind each router (I have tried several different workstations and they are all the same round trip times), however, when I ping Router B from Router A and vice versa, the round trip time remains 4ms.

Below are the "show version" and "show interfaces" outputs for each router:

ROUTER A#sh ver
Cisco Internetwork Operating System Software
IOS (tm) C1700 Software (C1700-K9O3SY7-M), Version 12.3(3g), RELEASE SOFTWARE (f                                                                              c1)
Copyright (c) 1986-2004 by cisco Systems, Inc.
Compiled Thu 20-May-04 23:01 by kellythw
Image text-base: 0x80008120, data-base: 0x8101FEC0

ROM: System Bootstrap, Version 12.2(7r)XM2, RELEASE SOFTWARE (fc1)

ROUTER A uptime is 4 weeks, 2 days, 23 hours, 15 minutes
System returned to ROM by reload
System image file is "flash:c1700-k9o3sy7-mz.123-3g.bin"

cisco 1721 (MPC860P) processor (revision 0x400) with 57236K/8300K bytes of memor                                                                              y.
Processor board ID FOC084917RG (1063469653), with hardware revision 0000
MPC860P processor: part number 5, mask 2
Bridging software.
X.25 software, Version 3.0.0.
1 FastEthernet/IEEE 802.3 interface(s)
1 Serial network interface(s)
WIC T1-DSU
32K bytes of non-volatile configuration memory.
32768K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

ROUTER A#sh int
FastEthernet0 is up, line protocol is up
  Hardware is PQUICC_FEC, address is 0012.8065.f331 (bia 0012.8065.f331)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, 100BaseTX/FX
  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 never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 367000 bits/sec, 189 packets/sec
  5 minute output rate 323000 bits/sec, 186 packets/sec
     286168409 packets input, 1861693242 bytes
     Received 8750723 broadcasts, 0 runts, 0 giants, 0 throttles
     69 input errors, 0 CRC, 0 frame, 69 overrun, 0 ignored
     0 watchdog
     0 input packets with dribble condition detected
     281527882 packets output, 279306152 bytes, 3 underruns
     3 output errors, 0 collisions, 6 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier
     0 output buffer failures, 0 output buffers swapped out
FastEthernet0.1 is up, line protocol is up
  Hardware is PQUICC_FEC, address is 0012.8065.f331 (bia 0012.8065.f331)
  Internet address is 192.168.10.1/24
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  1.
  ARP type: ARPA, ARP Timeout 04:00:00
  Last clearing of "show interface" counters never
FastEthernet0.2 is up, line protocol is up
  Hardware is PQUICC_FEC, address is 0012.8065.f331 (bia 0012.8065.f331)
  Internet address is 192.168.100.1/24
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  2.
  ARP type: ARPA, ARP Timeout 04:00:00
  Last clearing of "show interface" counters never
Serial0 is up, line protocol is up
  Hardware is PQUICC with Fractional T1 CSU/DSU
  Description: P2P 4.UHXX.204896
  Internet address is 10.1.1.1/24
  MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
     reliability 255/255, txload 12/255, rxload 6/255
  Encapsulation PPP, LCP Open
  Open: CDPCP, IPCP, loopback not set
  Last input 00:00:32, output 00:00:01, output hang never
  Last clearing of "show interface" counters 4w2d
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 2791
  Queueing strategy: priority-list 2
  Output queue (queue priority: size/max/drops):
     high: 0/20/0, medium: 0/40/0, normal: 0/60/2791, low: 0/80/0
  5 minute input rate 40000 bits/sec, 22 packets/sec
  5 minute output rate 76000 bits/sec, 24 packets/sec
     53416307 packets input, 3041339814 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     14 input errors, 5 CRC, 5 frame, 0 overrun, 0 ignored, 4 abort
     51316521 packets output, 4169747748 bytes, 0 underruns
     0 output errors, 0 collisions, 2 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up


ROUTER B#sh ver
Cisco Internetwork Operating System Software
IOS (tm) C1700 Software (C1700-K9O3SY7-M), Version 12.3(3g), RELEASE SOFTWARE (f                                                                              c1)
Copyright (c) 1986-2004 by cisco Systems, Inc.
Compiled Thu 20-May-04 23:01 by kellythw
Image text-base: 0x80008120, data-base: 0x8101FEC0

ROM: System Bootstrap, Version 12.2(7r)XM2, RELEASE SOFTWARE (fc1)

ROUTER B uptime is 1 year, 18 weeks, 5 days, 1 hour, 26 minutes
System returned to ROM by power-on
System image file is "flash:c1700-k9o3sy7-mz.123-3g.bin"

cisco 1721 (MPC860P) processor (revision 0x300) with 57236K/8300K bytes of memory.
Processor board ID FOC07480JB2 (4285813379), with hardware revision 0000
MPC860P processor: part number 5, mask 2
Bridging software.
X.25 software, Version 3.0.0.
1 FastEthernet/IEEE 802.3 interface(s)
1 Serial network interface(s)
WIC T1-DSU
32K bytes of non-volatile configuration memory.
32768K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

ROUTER B#sh int
FastEthernet0 is up, line protocol is up
  Hardware is PQUICC_FEC, address is 000e.8358.7829 (bia 000e.8358.7829)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, 100BaseTX/FX
  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 never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 106000 bits/sec, 75 packets/sec
  5 minute output rate 164000 bits/sec, 77 packets/sec
     972720728 packets input, 2651502650 bytes
     Received 33651907 broadcasts, 0 runts, 0 giants, 0 throttles
     3023 input errors, 0 CRC, 0 frame, 3023 overrun, 0 ignored
     0 watchdog
     0 input packets with dribble condition detected
     932515159 packets output, 4226292669 bytes, 13 underruns
     13 output errors, 0 collisions, 6 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier
     0 output buffer failures, 0 output buffers swapped out
FastEthernet0.1 is up, line protocol is up
  Hardware is PQUICC_FEC, address is 000e.8358.7829 (bia 000e.8358.7829)
  Internet address is 192.168.20.1/24
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  1.
  ARP type: ARPA, ARP Timeout 04:00:00
  Last clearing of "show interface" counters never
FastEthernet0.2 is up, line protocol is up
  Hardware is PQUICC_FEC, address is 000e.8358.7829 (bia 000e.8358.7829)
  Internet address is 192.168.200.1/24
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  2.
  ARP type: ARPA, ARP Timeout 04:00:00
  Last clearing of "show interface" counters never
Serial0 is up, line protocol is up
  Hardware is PQUICC with Fractional T1 CSU/DSU
  Description: P2P 4.UHXX.204896
  Internet address is 10.2.2.2/24
  MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
     reliability 255/255, txload 12/255, rxload 21/255
  Encapsulation PPP, LCP Open
  Open: CDPCP, IPCP, loopback not set
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 1y18w
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 138649
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 130000 bits/sec, 53 packets/sec
  5 minute output rate 76000 bits/sec, 52 packets/sec
     715908630 packets input, 4116564358 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     2390 input errors, 449 CRC, 1618 frame, 0 overrun, 0 ignored, 323 abort
     739474065 packets output, 1900206779 bytes, 0 underruns
     0 output errors, 0 collisions, 29 interface resets
     0 output buffer failures, 0 output buffers swapped out
     7 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up


Any ideas as to why this is now happening?
[+][-]11/06/09 08:58 PM, ID: 25765053Expert Comment

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