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2821 High Interface Discards - RP Drops??

dkuchenski
Level 1
Level 1

I am having an issue pinpointing why my 2821 router is discarding so many packets when transferring data to our second site.  The traffic flows from the local lan, to the router, where it is redirected via WCCP to a WAN optimization device, back to the router and over a GRE tunnel to the second site where the same process happens.  The traffic does get there, but the LAN/Repeater router interfaces have around 20,000-60,000 input drops an hour.  From the output below, it looks like traffic is being dropped by the RP, but I'm not sure why.

Drawing2.jpg

I just restarted the router as a last resort, and here is what has accumulated in the last 30 min:

FastEthernet0/0/1 is up, line protocol is up

  Hardware is Fast Ethernet, address is 0025.840c.7680 (bia 0025.840c.7680)

  Description: REPEATER

  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,

     reliability 255/255, txload 99/255, rxload 94/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input never, output never, output hang never

  Last clearing of "show interface" counters never

  Input queue: 0/75/40341/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 37049000 bits/sec, 5810 packets/sec

  5 minute output rate 38928000 bits/sec, 5909 packets/sec

     12324124 packets input, 855031048 bytes, 0 no buffer

     Received 211 broadcasts (0 multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

     0 watchdog, 0 multicast, 0 pause input

     0 input packets with dribble condition detected

     12912889 packets output, 1892021583 bytes, 0 underruns

     0 output errors, 0 collisions, 2 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

ROUTER#show int fa0/0/1 switching | i Drops

                   Drops         RP      41172         SP          0

            SPD Priority     Inputs          0      Drops          0

And the interface is an access interface to VLAN10, so I'm not sure if this is normal:

FastEthernet0/0/1

          Switching path    Pkts In   Chars In   Pkts Out  Chars Out

               Processor   12729585 1202817196   13308563 2202992366

             Route cache          0          0          0          0

                   Total   12729585 1202817196   13308563 2202992366

Vlan10

          Switching path    Pkts In   Chars In   Pkts Out  Chars Out

               Processor        682      91136        492      86741

             Route cache   13039220 1439804318   13686842 2420832659

                   Total   13039902 1439895454   13687334 2420919400

And CPU never goes above 40%

  100

   90

   80

   70

   60

   50

   40 ****     ***************          *****          *****

   30 ************************************************************

   20 ************************************************************

   10 ************************************************************

     0....5....1....1....2....2....3....3....4....4....5....5....6

               0    5    0    5    0    5    0    5    0    5    0

               CPU% per second (last 60 seconds)

      3343344334333334343333344334334432222221 22122   1

      982990088079788082987890096189014653234940181655467474453743

  100

   90

   80

   70

   60

   50

   40 *##*########***####**#*#*#*#*###

   30 #################################**          *

   20 #######################################* **###   *

   10 ######################################## #####** ** *  * *

     0....5....1....1....2....2....3....3....4....4....5....5....6

               0    5    0    5    0    5    0    5    0    5    0

               CPU% per minute (last 60 minutes)

              * = maximum CPU%   # = average CPU%

Hopefully someone can help me with this, thanks!

17 Replies 17

Unfortunately I don't have a service contract on that router, but I think I just solved the issue!

I switched the port my Branch Repeater is using from the fa0/0/1 HWIC-4ESW port to an integrated Gi0/1 port, and no more drops!  I did some research and found the HWIC-4ESW has max bandwidth capibility of 100Mbps for all 4 ports, and that could even drop depending on other services used.

I think I'm going to move another link off that 4ESW card and get a HWIC-2FE, the 2821 should be able to run both cards together, right?  I would have a total of 4 routable interfaces, and one routable SVI...with about 40Mbps in/20Mbps out of WAN bandwidth and some LAN traffic running through the router.

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Fantastic!  I hadn't noticed nor thought to ask what kind of Ethernet this port was.

Yes, a HWIC-4ESW might very much explain a performance issue; which seems to be confirmed by you moving to a built-in gig port.

Besides the limitations of the 4ESW, the HWIC also has limited capacity too, although enough to support single or dual HWIC-#FE.

If you have a switch that supports trunking, you might also consider using subinterfaces on a built-in gig port, and save the expense of buying another module.

Yes, I could trunk to the gig interface, good idea.

Thanks for all the help!

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