"Show interface VLAN" and Multicast Traffic

aletat0ne · ‎12-13-2010

Hi Gents,

I hope someone of you could help me.

I have 2 VLANs in my network rightly configured with pim (sparse-dence-mode).

In this 2 VLANs there is lot of multicast traffic and the multicast routing between vlans is working properly.

But when i type "show interface VLAN" I get some very strange value of traffic...

For instance:

Multicast Source in VLAN 10 (25megabits of traffic)

Receiver in VLAN 20

If I do "show interface vlan 10" I get the follow:

6506E-CS1-CORE#sh int vlan 10

Vlan10 is up, line protocol is up

Hardware is EtherSVI, address is

Internet address is

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

reliability 255/255, txload 1/255, rxload 6/255

Encapsulation ARPA, loopback not set

Keepalive not supported

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

Last input 00:00:01, output 00:00:02, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/19/19 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 25028000 bits/sec, 2291 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

L2 Switched: ucast: 1036 pkt, 69072 bytes - mcast: 679269098 pkt, 906330264325 bytes

L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 5960221256 pkt, 8127597456186 bytes mcast

L3 out Switched: ucast: 9729 pkt, 2535765 bytes mcast: 8690750333 pkt, 11857610863658 bytes

6258337235 packets input, 8529846060405 bytes, 0 no buffer

6506E-CS1-CORE#sh int vlan 20

Vlan20 is up, line protocol is up

Hardware is EtherSVI, address is

Internet address is

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

reliability 255/255, txload 1/255, rxload 10/255

Encapsulation ARPA, loopback not set

Keepalive not supported

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 never

Input queue: 0/75/12568301/12351485 (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

L2 Switched: ucast: 1251997827 pkt, 1179775309804 bytes - mcast: 410380869 pkt, 545148498927 bytes

L3 in Switched: ucast: 1206517537 pkt, 309968572374 bytes - mcast: 15440864209 pkt, 21030454959390 bytes mcast

L3 out Switched: ucast: 1927289505 pkt, 2069394447179 bytes mcast: 3185128542 pkt, 4342220954182 bytes

As you can see in red, it seems that the comand ignored multicast routed traffic.

Is it correct? is there a way to see the multicast routed traffic input and output rate?

Can some one of you show me a document with the theory about it?

Last one consideration, when I check VLAN graphics in Cacti or Nagios, they show me

complitely different result from "show interface vlan"... do you know why?

Thank you very much

Alex

Yogesh Ramdoss · ‎12-13-2010

Alessandro,

Let me try to help you with limited information provided.

When we issue "sh interface vlan X", the "5 minute input rate" and "5 minute output rate" provided

only the traffic sent to CPU (means, sent to control-plane for some reason).

Looks like, traffic received in vlan 10 is sent to CPU (at 2291 pkts/sec) for some reason. To know,

you need to SPAN RP Inband and analyze the traffic sent to CPU.

To know the total multicast traffic sent/received on a vlan, please look at the counters reproted for

L3-Switched traffic.

6506E-CS1-CORE#sh int vlan 10 <<== vlan 10
Vlan702 is up, line protocol is up <<== Vlan 702 ?!?!?! very confusing
L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 5960221256 pkt, 8127597456186 bytes mcast
L3 out Switched: ucast: 9729 pkt, 2535765 bytes mcast: 8690750333 pkt, 11857610863658 bytes

Hope this helps.

Regards,

Yogesh

aletat0ne · ‎12-13-2010

Thank You very much Yogesh,

first of all I did a mistake with copy and paste so sorry for:

6506E-CS1-CORE#sh int vlan 10 <<== vlan 10
Vlan702 is up, line protocol is up <<== Vlan 702 ?!?!?! very confusing

Now I have correct it.

I forgot to tell you that I'm using a Switch Cisco 6504 ios Version 12.2(33).

The reason I opened this post is because I noticed a difference between Cacti Graphic for Int Vlan 20

and Show interface vlan 20.

So I wondered why I didn't see traffic in output rate for Vlan20, I know that there is an host in Vlan20 that

is receiving 25megabit multicast traffic from Vlan10 (multicast routed in c6504 using pim).

How can I see this "output bit rate" in Vlan 20?

Thanks

Ale

Yogesh Ramdoss · ‎12-13-2010

Alessandro,

Thanks for correcting the command results.

I do not think Cat6500 maintains a counter to report input/output rate of hardware-switched traffic per-vlan basis.

I guess, the SNMP application find the difference (in the number of multicast packets) between two successive pollings, and tell you the rate.

For e.g.,

At 1st polling ==> counter = 1000

At 2nd polling (done after 1 second) ==> counter = 2000

Then the rate = (2000-1000)/1 sec = 1000 pkts/sec

"show mls statistics mod X" provides you total number of L3-Switched traffic by specific module/EARL X, again not per-vlan basis.

- Yogesh