Archive for December, 2010|Monthly archive page


In Uncategorized on December 29, 2010 at 22:07

With the holidays and such, and now that I am sick – I have ignored this blog for a little bit. I promise I will get something good up soon. Need to focus on those VRF labs and get them published soon.

I promise…


March 11, 2011 – Tick-tock goes the clock

In Uncategorized on December 7, 2010 at 16:45

The clock is ticking and time is running out. Just submitted my CC to Cisco for the CCIE SP Lab payment. Guess it only a few months until I see San Jose, CA and the Cisco campus. Tick-tock.

Cisco ASR and LACP

In Uncategorized on December 2, 2010 at 11:50

I am currently working on a new site deployment utilizing some Cisco ASR1002 routers.  When we typically design a location we cross-connect the two WAN routers via a cross-over cable; this allows us to have the capability to continue to transit traffic over the connected WAN routers and WAN links if need to take down the Core at the site for maintenance.

If you look at the image below you will see three Sites – A – B – C.  Traffic that is destined to Site B from Site A will transit the connected WAN link.  So what happens if that WAN link goes down, it will transit through Site C instead.  By having the WAN routers connected via a cross-over cable, the traffic will stay at the end and not transverse the internal LAN of the site.

Ok, the background information is now out of the way. Lets continue.

Typically we use a single gigabit ethernet cross-over cable between the routers, due to hardware limitations. Well, with the ASR series we now have more interfaces that we can use for this connectivity.  What I have also found is that the ASR and IOS-XE support LACP and etherchannels.  This is a wonderful thing as it actually solves some of the problems of a single cross-over cable between routers.

So, how does one configure LACP on the ASR 1002?  It is done the same way as you would on the Nexus for L3 etherchannel. Below are the configuration commands as well as the ways to check.

For this example, we are going to create Port-Channel 12 on the router and assign interfaces G0/0/2 and G0/0/3 to the channel-group

Router#conf t
Router(config)#interface GigabitEthernet0/0/2
Router(config-if)# channel-group 12 mode active
Router(config-if)# no shut
Router(config-if)# exit
Router(config)#interface GigabitEthernet0/0/3
Router(config-if)# channel-group 12 mode active
Router(config-if)# no shut
Router(config-if)# exit

Now we can configure an IP address on the port-channel interface:
Router(config)#interface Port-channel12
Router(config-if)# ip address

T0 check the port-channel:

Router#sh int port-channel 12
Port-channel12 is up, line protocol is up
Hardware is GEChannel, address is c471.fe0c.55cb (bia c471.fe0c.55cb)
Internet address is
MTU 1500 bytes, BW 2000000 Kbit/sec, DLY 10 usec,

You can also look at the LACP information:

Router#sh lacp 12 neighbor
Flags:  S – Device is requesting Slow LACPDUs
F – Device is requesting Fast LACPDUs
A – Device is in Active mode       P – Device is in Passive mode

Channel group 12 neighbors

Partner’s information:

Partner Partner   LACP Partner  Partner   Partner  Partner     Partner
Port      Flags   State     Port Priority Admin Key Oper Key Port Number Port State
Gi0/0/2   SA      bndl      32768         0x0       0xC      0x3         0x3D
Gi0/0/3   SA      bndl      32768         0x0       0xC      0x4         0x3D

Now lets ping to test:

Router#p t 1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 1 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

If you noticed I typed t 1 – that means use a 1 second timeout.  I did that in case, for some reason, it does not PING successfully I only have to wait half the normal time of 2 seconds per ping.  This might not seem like a big deal, but if you use this on some LAB test – you can save some time and frustration. 🙂

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