Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Community Member

Traceroute inconsistency from one switch

Can anyone tell me why I am getting these inconsistent traceroute results from

one switch? Why does switch 172.23.31.8 trace fine to 172.23.30.1 but switch

172.23.31.6 is sent to the default route when tracing to 172.23.30.1 ?

See attached diagram. Thanks!

Everyone's tags (3)
5 REPLIES
Community Member

Traceroute inconsistency from one switch

Anyone? Bueller?

Traceroute inconsistency from one switch


Can u share config.  There might be routes issue.

Jawad

Jawad
Community Member

Traceroute inconsistency from one switch

The routing table looks normal. Switch 172.23.31.6 was recently replaced

due to hardware failure, and this strange behaviour seems to have started

with that replacement. Not sure what the problem is. Thanks.

show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is 172.23.31.1 to network 0.0.0.0

C       172.23.31.0 is directly connected, Vlan1

     172.23.0.0/24 is subnetted, 2 subnets

D       172.23.30.0 [90/3072] via 192.168.2.2, 7w0d, Port-channel1

     10.0.0.0/24 is subnetted, 7 subnets

D       10.90.155.0 [90/3072] via 192.168.2.21, 7w0d, Port-channel2

         .

         .

     192.168.2.0/30 is subnetted, 8 subnets

C       192.168.2.0 is directly connected, Port-channel1

C       192.168.2.20 is directly connected, Port-channel2

         .

         .

S*   0.0.0.0/0 [1/0] via 172.23.31.1

Also, an updated diagram that fixes one typo.

Traceroute inconsistency from one switch

Port connecting the new switch to that router, can you verify that they are configured correctly and match the settings on the router i.e duplex, speed etc.  Also 172.23.31.1 firewall can you make sure that it is still not caching the mac of old switch still by any chance, you might have to clear that out.  Other than the trace route do you have any performance issues on the clients that are connected to the 172.23.31.6 switch?

Community Member

Traceroute inconsistency from one switch

Switch ports look normal in all aspects. See below.

On the firewall, I don't see any ARP entries for the 172.23.31.6 or 172.23.31.8 switches

probably because those specific IPs don't often traverse that firewall for anything.

I see ARPs for clients connected to the 172.23.31.6 switch, though.

Yes, we are not able to connect to clients on the 172.23.30.0 subnet from

clients on the 172.23.31.6 switch (like with VLC or Dameware) because the packets

are being diverted to the firewall along the way and the firewall does not allow those

signals. The firewall does redirect pings and traceroute back to 172.23.31.4 however

because it does allow those and sends them back via a static route it has to the

172.23.30.0 subnet. I don't know why the router is getting confused about where to

forward packets from this one switch. Why is it sending them to it's default gateway

instead of what it knows in the routing table ???

Thanks for considering this strange issue...

Switch#sh run (excerpt)

interface GigabitEthernet0/52

switchport trunk encapsulation dot1q

switchport mode trunk

srr-queue bandwidth share 1 30 35 5

priority-queue out

mls qos trust cos

auto qos trust

macro description cisco-switch

spanning-tree link-type point-to-point

Switch#sh int Gi0/52

GigabitEthernet0/52 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet, address is

  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive not set

  Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseLX SFP

  input flow-control is off, output flow-control is unsupported

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

  Last input 00:00:11, 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)

Router#sh run (excerpt)

interface GigabitEthernet1/0/52

switchport trunk encapsulation dot1q

switchport mode trunk

srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape  10  0  0  0

queue-set 2

mls qos trust cos

macro description cisco-switch

auto qos voip trust

spanning-tree link-type point-to-point

Router#sh int GigabitEthernet1/0/52

GigabitEthernet1/0/52 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet, address is

  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive not set

  Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseLX SFP

  input flow-control is off, output flow-control is unsupported

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

  Last input 00:00:08, output 00:00:19, 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)

757
Views
0
Helpful
5
Replies
CreatePlease to create content