Ethernet Switching
Ethernet Switching

Connecting MX5 and Cisco 3750 - Lots of runts

06.12.12   |  
‎06-12-2012 07:35 AM

I'm trying to connect a MX5 router with a 3750 with a layer 3 VLAN using a copper SFP on the MX5.  The ports come up fine on Layer1, but the 3750 is showing that all incoming packets are errors/runts:



3750#show int gi1/0/3
GigabitEthernet1/0/3 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0016.c85b.c483 (bia 0016.c85b.c483)
  MTU 1500 bytes, BW 1000000 Kbit, 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 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  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: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     0 packets input, 832 bytes, 0 no buffer
     Received 0 broadcasts (0 multicasts)
     17 runts, 0 giants, 0 throttles
     17 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     109 packets output, 6976 bytes, 0 underruns
     0 output errors, 0 collisions, 6 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



R1# run show interfaces ge-1/1/8
Physical interface: ge-1/1/8, Enabled, Physical link is Down
  Interface index: 158, SNMP ifIndex: 534
  Link-level type: Ethernet, MTU: 1518, Speed: 1000mbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Enabled, Auto-negotiation: Enabled,
  Remote fault: Online
  Device flags   : Present Running Down
  Interface flags: Hardware-Down SNMP-Traps Internal: 0x0
  CoS queues     : 8 supported, 8 maximum usable queues
  Current address: 5c:5e:ab:d6:dc:80, Hardware address: 5c:5e:ab:d6:dc:80
  Last flapped   : 2012-06-12 09:28:54 EDT (00:00:12 ago)
  Input rate     : 0 bps (0 pps)
  Output rate    : 0 bps (0 pps)
  Active alarms  : LINK
  Active defects : LINK
  Interface transmit statistics: Disabled

  Logical interface ge-1/1/8.0 (Index 335) (SNMP ifIndex 542)
    Flags: Device-Down SNMP-Traps 0x0 VLAN-Tag [ 0x8100.649 ]  Encapsulation: ENET2
    Input packets : 0
    Output packets: 17
    Protocol inet, MTU: 1500
      Flags: Sendbcast-pkt-to-re
      Addresses, Flags: Dest-route-down Is-Preferred Is-Primary
        Destination: 10.64.9/24, Local:, Broadcast:
    Protocol multiservice, MTU: Unlimited

  Logical interface ge-1/1/8.32767 (Index 336) (SNMP ifIndex 543)
    Flags: Device-Down SNMP-Traps 0x0 VLAN-Tag [ 0x0000.0 ]  Encapsulation: ENET2
    Input packets : 0
    Output packets: 0
    Protocol multiservice, MTU: Unlimited
      Flags: None


It's outputting packets to the MX5, but the MX5 doesn't see any input packets.  I did some research and found that runts generally have something to do with a duplex mismatch or a link being half-duplex.  I've tried manually setting the speed and duplex on both devices, as well as trying to turn off/on auto-negotiation to no avail.  Does anyone know why this is happening?  Below are the port configs for both:


interface GigabitEthernet1/0/3
 switchport access vlan 649
 switchport mode access
 no cdp enable
interface Vlan649
 ip address
 no ip proxy-arp




R1# show interfaces ge-1/1/8
unit 0 {
    vlan-id 649;
    family inet {

Ethernet Switching

Re: Connecting MX5 and Cisco 3750 - Lots of runts

06.12.12   |  
‎06-12-2012 04:35 PM

for starters it looks like you have the Cisco side as an access port, but the Juniper side is tagged