[c-nsp] Odd Ethernet Behavior and Interface Counters

[Michael K. Smith]

Hello All:

We have recently installed a GSR with a 3-port GigE line card.  Only one of
the ports is in use and it connects to a Catalyst 3550 in layer-2 mode.  We
are seeing two issues that may be completely unrelated, but we're at a loss
to tell.  Any help or insights would be greatly appreciated.

The issues are, 1) connectivity issues to some subnets but not others and,
2) lots of Giants on the interface on the GSR side.  The second issue is odd
because there is no device anywhere in the network sending frames larger
than 1500 bytes and the system mtu is set to 1500 on the 3550.  As you can
imagine, there are no errors on the 3550-side.  As for the multicast, I can
only assume that's HSRP working as there are quite a few sub-interfaces on
the GSR Gig port for HSRP groups.

Here is what a traceroute looks like from the GSR to a device connected off
a switch connected ultimately to the 3550.

Tracing the route to xxx

  1  ?  ?  ? 
  2  ?  ?  ? 
  3  *  ?  ? 
  4  ?  * 

Pings get through with no trouble.

The second issue is the counters on the GigE port on the GSR.  I've included
config snippets and "sho int" from both sides of the connection.

GSR:

interface GigabitEthernet0/0
 description Uplink
 ip address x.x.x.x 255.255.255.248
 no ip directed-broadcast
 no negotiation auto

GigabitEthernet0/0 is up, line protocol is up
  Hardware is GigMac 3 Port GigabitEthernet, address is 0003.a01b.4000 (bia
0003.a01b.4000)
  Description: Uplink ot sea-csw0/s0/p1
  Internet address is x.x.x.x/29
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, rely 255/255, load 13/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full Duplex, 1000Mbps, link type is force-up, media type is SX
  output flow-control is unsupported, input flow-control is unsupported
  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 02:03:26
  Queueing strategy: fifo
  Output queue 0/40, 0 drops; input queue 0/75, 0 drops
  5 minute input rate 161389000 bits/sec, 20416 packets/sec
  5 minute output rate 51105000 bits/sec, 16578 packets/sec
     153982848 packets input, 148831716397 bytes, 0 no buffer
     Received 81408 broadcasts, 0 runts, 19969765 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 1654495 multicast, 0 pause input
     122125511 packets output, 36787730021 bytes, 0 underruns
     Transmitted 10763 broadcasts
     0 output errors, 0 collisions, 0 interface resets
     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

On the 3550

interface GigabitEthernet0/1
 description Uplink
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 17
 switchport mode trunk
 switchport nonegotiate
 speed nonegotiate

GigabitEthernet0/1 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 000a.f472.a801 (bia
000a.f472.a801)
  Description: Uplink to sea-cor0/s0/p0
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 41/255, rxload 13/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is SX
  input flow-control is off, output flow-control is off
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:13, 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 53164000 bits/sec, 16734 packets/sec
  5 minute output rate 163741000 bits/sec, 20673 packets/sec
     1414965791 packets input, 76037141 bytes, 0 no buffer
     Received 6175071 broadcasts (0 multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 6016213 multicast, 0 pause input
     0 input packets with dribble condition detected
     2546834074 packets output, 2574303238 bytes, 0 underruns
     0 output errors, 0 collisions, 3 interface resets
     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