cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Announcements
Join Customer Connection to register!
736
Views
0
Helpful
4
Replies
Colin Higgins
Explorer

WAN congestion causing interface resets?

I have a router with a multilinked (2) T1 bundle that connects to a MPLS network.

I am using BGP as my routing protocol.

I am having problems in this site and others with carrier transitions, crc errors, input errors, frame errors, and output drops. It is not uncommon for link utilization to go up to 99% during backups, and my provider (AT&T) is claiming that over-utilization is causing the interface to go down (reset).

Here is what the physical interface looks like (note the errors):

Serial0/0/0 is up, line protocol is up
  Hardware is GT96K with integrated T1 CSU/DSU
  MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
     reliability 255/255, txload 8/255, rxload 15/255
  Encapsulation PPP, LCP Open, multilink Open
  Link is a member of Multilink bundle Multilink1, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 2w6d
  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 94000 bits/sec, 44 packets/sec
  5 minute output rate 50000 bits/sec, 44 packets/sec
     106372481 packets input, 1579483919 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     145 input errors, 145 CRC, 66 frame, 37 overrun, 0 ignored, 102 abort
     141062298 packets output, 2551614815 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

and the multilink is:

Multilink1 is up, line protocol is up
  Hardware is multilink group interface
  Internet address is XXXX
  MTU 1500 bytes, BW 3072 Kbit, DLY 100000 usec,
     reliability 255/255, txload 8/255, rxload 18/255
  Encapsulation PPP, LCP Open, multilink Open
  Listen: CDPCP
  Open: IPCP, loopback not set
  Keepalive set (10 sec)
  DTR is pulsed for 2 seconds on reset
  Last input 00:00:00, output never, output hang never
  Last clearing of "show interface" counters 2w6d
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 40935
  Queueing strategy: Class-based queueing
  Output queue: 0/1000/64/40935 (size/max total/threshold/drops)
     Conversations  0/77/256 (active/max active/max total)
     Reserved Conversations 2/2 (allocated/max allocated)
     Available Bandwidth 194 kilobits/sec
  5 minute input rate 222000 bits/sec, 86 packets/sec
  5 minute output rate 99000 bits/sec, 77 packets/sec
     198903171 packets input, 3903303225 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     83 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     267648768 packets output, 2917984847 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transition

I do have WAN QoS enabled. The policies are:

policy-map wanqos
class voice
  priority 2000
  set dscp ef
class cos2
  bandwidth 54
  set dscp af31
class stuntraffic
  bandwidth 56
  set dscp af41
class class-default
  set ip dscp default
  fair-queue
policy-map qos_outbound
class enhanced_qos
  bandwidth 56
  set ip dscp af31
class class-default
  set ip dscp default

class-map match-all enhanced_qos
match access-group name enhanced_qos_map
class-map match-all cos3
match  dscp af21
class-map match-any cos2
match access-group name voice-control
match  dscp af31
match  precedence 3
class-map match-all stuntraffic
match access-group 100
class-map match-all voice
match access-group name voice

Is it possible for congestion on this interface to actually cause the entire thing to go down (flapping basically)?

4 REPLIES 4
rassoul.ghaznavi
Beginner

Hi,

In some circumstances, yes it is possible,

What I would do  is enable ip nbar protocol-discovery and find out what is happening on the interface and what traffic it that.

Network Group

Kishore Chennupati
Rising star

Hi,

When you say resets, are you talking about the physical resets because I dont see any from your output. All the errors you are talking about can be due to physical issues like bad cabling between the NTU and the router and also due to the max-utilisation and your router is not able to keep up.

Did you try shaping?

 

Here is what the physical interface looks like (note the errors):

Serial0/0/0 is up, line protocol is up
  Hardware is GT96K with integrated T1 CSU/DSU
  MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
     reliability 255/255, txload 8/255, rxload 15/255
  Encapsulation PPP, LCP Open, multilink Open
  Link is a member of Multilink bundle Multilink1, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 2w6d
  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 94000 bits/sec, 44 packets/sec
  5 minute output rate 50000 bits/sec, 44 packets/sec
     106372481 packets input, 1579483919 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     145 input errors, 145 CRC, 66 frame, 37 overrun, 0 ignored, 102 abort
     141062298 packets output, 2551614815 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets             
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

and the multilink is:

Multilink1 is up, line protocol is up
  Hardware is multilink group interface
  Internet address is XXXX
  MTU 1500 bytes, BW 3072 Kbit, DLY 100000 usec,
     reliability 255/255, txload 8/255, rxload 18/255
  Encapsulation PPP, LCP Open, multilink Open
  Listen: CDPCP
  Open: IPCP, loopback not set
  Keepalive set (10 sec)
  DTR is pulsed for 2 seconds on reset
  Last input 00:00:00, output never, output hang never
  Last clearing of "show interface" counters 2w6d
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 40935    <<< not good
  Queueing strategy: Class-based queueing
  Output queue: 0/1000/64/40935 (size/max total/threshold/drops)
     Conversations  0/77/256 (active/max active/max total)
     Reserved Conversations 2/2 (allocated/max allocated)
     Available Bandwidth 194 kilobits/sec
  5 minute input rate 222000 bits/sec, 86 packets/sec
  5 minute output rate 99000 bits/sec, 77 packets/sec
     198903171 packets input, 3903303225 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     83 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     267648768 packets output, 2917984847 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transition


HTH,

Regards

Kishore

Please rate if helpful

I cleared the counters after getting the interface resets and carrier transitions: that's why they don't appear here.

But I have been getting them in several locations on this MPLS network.

Congestion occurs because of large data transfers between databases mostly. The QoS policies obviously prioritize voice over the WAN (which is necessary).

I'm not sure how traffic shaping would fit in with the QoS policies I have enabled

meperuma
Beginner

Hi interface reset may happen due to missing l2 keepalives also, looking at the output, the physical layer may not be good.

Worth to look at mlppp statistics also.

Sent from Cisco Technical Support iPhone App