Home > SROS > SROS Interface Configuration – 7750

SROS Interface Configuration – 7750

In this post I will focus on creating interfaces so it will be a short one because there isn’t much to write home about.

The first thing to know about SROS interfaces is they are named and you bind a physical or logical port to them.  The naming of the interface is called in all protocols so you need to make sure you get it right and have a clear convention as deleting the interface will destroy the protocols use of the interface.  If you have an OSPF interface and you remove the router interface then OSPF will drop and your network maybe go a little crazy.

So how do we configure them?  It’s pretty straightforward and there is no need to create here. Good ol’ ALU consistency.


*A:pe1# configure router interface "to_pe2"

And that’s the interface created. We then need to assign our IP address:


*A:pe1>config>router>if$ address 192.168.123.1/24

You can also run ipv6 over interfaces, which is enabled with the ipv6 command. You need to be in chassis mode C at a minimum and I can’t change that right now…You can do pretty much anything standard, icmp6, DHCP, VRRP.

Then we need to bind this to a physical interface:


*A:pe1>config>router>if$ port 2/1/3:123

Next you might want to run BFD over the interface to use very fast failure detection. The 7750 can be configured to support 10ms transmit intervals but it does require configuration relating to the processor. I have never tried it that low so I dont know what impact it will have on processing.


*A:pe1>config>router>if$ bfd 100 receive 100 multiplier 3

You can assign some CPM protection but I haven’t played with this either so I don’t know how it would benefit you. Something for another time when days allow more than 24 hours in them!

If you want, make the interface a loopback but obviously you need to remove your port binding with the no port command.

If you wish to make it an unnumbered interface you simply configure it with unnumbered and specify an interface name or address you want to take the IP address from.

To configure a secondary interface you simply apply secondary x.x.x.x/y

Finally you can configure VRRP with all the standard bits and bobs that entails. Here is a little snippet that creates the interface as the owner, specifies the partner router as .3, sets the priority to 200 so this interface will be the boss unless there is a problem. You can also tell the interface to reply to pings and traces regardless of it’s state as master or backup which is a pretty cool feature. Finally you can set the delay VRRP takes before establishing for situations where you have a link that may be bouncing.


*A:pe1>config>router>if$ vrrp 1 owner
*A:pe1>config>router>if>vrrp$ backup 192.168.123.3
*A:pe1>config>router>if>vrrp$ priority 200
*A:pe1>config>router>if>vrrp$ ping-reply
*A:pe1>config>router>if>vrrp$ traceroute-reply
*A:pe1>config>router>if>vrrp$ init-delay 10

There are some things you can do with BFD in a VRRP instamce but that will have to wait to my Services posts as it’s more relevant here. Anyway today is day 1 of my CCIE SP study so I have to get down to business there.

Categories: SROS
  1. Naveen Jindal
    August 6, 2014 at 11:32 am

    how do I bypass the traffic to another address incase the BFD does not receive any packets within the specified time period ?
    Thank You.

    • iamjeffvader
      August 6, 2014 at 8:42 pm

      Hi Naveen, I don’t follow what you mean? If you have two paths to a prefix and path A is costed better than path B then A is used. If BFD is configured and registered with your IGP interfaces, failure to receive hellos within the tx/rx X multiplier time frame over link A means the adjacency of A will be declared down and the IGP will reconverge to use link B. Is this what you mean? You don’t have to specify anything further as BFD is just a means to signal a failure rapidly and efficiently.

      • Naveen Jindal
        August 8, 2014 at 10:55 am

        Actually, I have a router with BFD enabled on it and with two interface. It first communicates with interface 1 and if it does not receive any response, it must automatically communicate with the second interface.
        Thank You

      • iamjeffvader
        August 8, 2014 at 10:59 am

        Sorry still don’t follow what you mean. Can you post configs and maybe an ascii diagram?

      • Naveen Jindal
        August 8, 2014 at 11:22 am

        http://www.asciidraw.com/#Draw7367625144383223166

        this is the link. The client requests for some content. The router first contacts with server1 and if it is down, it must contact with server2 for the same content. I hope You have understood what I mean.
        Thank You.

      • iamjeffvader
        August 8, 2014 at 11:31 am

        I presume the servers support BFD? If you are routing to then statically you need to enable BFD on the interface and then on the static route, the same as you would with an IGP interface.
        If the server doesn’t support BFD then you’re better off doing a cpe ping on your static route.

  2. Naveen Jindal
    August 11, 2014 at 3:37 am

    Okay. Thank you so much. I will try the same and get back to you.

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