29 Apr

Virtual IP, MgmtEth interfaces and switchover on ASR9k

On ASR9000 router you have two RSP’s, both with MgmtEth0 interfaces. Interfaces on both of RSP’s have to be in the same subnet, what more a Virtual IP address, that is in the same subnet as MgmtEth0’s interfaces have to be configured. So technically you may think that you have three out-of-band management entry points to the router. This is unfortunately false.
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27 Apr

Getting familiar with IOS XR

I’m getting familiar with ASR9k routers and IOS XR right now at the training in Cisco HQ. IOS XR is different. It’s modular, it have slightly different fordesigns that traditional IOS or IOS XE, which is more or less IOS converted as a Linux process on ASR1k.
For those familiar with JunOS CLI and programming new IOS XR might be easier to use than traditional IOS CLI. You can prepare your configuration ahead, review it and commit all the changes at once. To bad Cisco didn’t implement commit check command like on JunOS that let you test if configuration that you’re going to commit is consistent. Another big disadvantage – when you execute show configuration changes diff you can see changes that will be made to running-config when you commit your changes. Diff looks quite similar to one you know from UNIX platforms. Except the fact that both lines that will be unchanged or removed are preceded with “-“, while lines that be added to configuration are preceded with “+”. Not really clear to tell what you remove and what not. But you can always perform show configuration changes to look how your configuration will look like after commit.

12 Apr

Passing username in CUBE-SP

By default when register message passes SBC username in contact field is replaced with random string. This string identifies pinhole opened for particular user for management purposes. But this behavior is not always desirable. Many SIP implementations identifies user by Contact field and rewriting it with random string would prevent application from registration.
SBC can be configured to pass username set in Contact field. To do this you have to configure

    registration contact username passthrough

This have to be set on adjacency that should not rewrite username when SIP REGISTER comes from

06 Apr

DHCPv6 service

On IOS routers you can disable built-in DHCP server issuing command

no service dhcp

you should expect that it will disable whole DHCP service no matter what protocol it’s going to service. Wellm you are wrong. It disable only IPv4 DHCP service leaving IPv6 one still running. Therefor following configuration

ipv6 dhcp pool IPv6
 dns-server FC00:2::D911:220A
!
interface GigabitEthernet0/0
  ipv6 address FC00:3::1/64
  ipv6 nd other-config-flag
  ipv6 dhcp server IPv6

will still work and built-in DHCP server will assign DNS information to requesting IPv6 host.

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