Author Archives: Darren

The Accumulated IGP Metric Attribute for BGP

This is an interesting draft which can ensure better paths are chosen in certain corner cases. Before this draft, BGP was able to redistribute the IGP metric as a MED value into BGP. The issue with MED is that it’s very low on the BGP best path algorithm. Note that Cisco/Brocade consider weight as primary, […]

Segment Routing on IOS-XR

Cisco has released some support for segment-routing on IOS-XR 5.2.0 so what better time to lab it up. I’ve got four IOS-XRv boxes running 5.2.0: RP/0/0/CPU0:XR1#sh ver | include XR Cisco IOS XR Software, Version 5.2.0[Default] Currently IS-IS is the only protocol with support in XR. There are drafts to get this working in both […]

OSPF Enhancements in recent IOS versions

OSPFv3 Authentication Trailer In 2011 I wrote an article showing that in order to provide authenticated OSPFv3 neighbour sessions, you needed the security license on IOS. Manav Bhatia commented on that post stating they were working on an IETF standard to fix this. That draft became RFC6506 and then RFC7166 Cisco has added support for […]

Juniper EX – Private vlans

I’ve gone over pvlans before on IOS, so I’m going to cover Juniper’s implementation today. This post will be based on the following topology: There are five hosts and a single router. Host1 and Host3 are in the same community vlan, while Host2, Host4, and Host5 are in isolated vlans. R1 is the default gateway […]

Juniper EX Virtual-Chassis notes

I’ve been deploying some EX VCs recently so this post will go over some configuration and verification commands. To start with I have two EX4200s in my lab connected via the built-in VC ports. I’m running code version 12.3R6.6 VC Ports When booting this type of configuration, the switches will automatically attempt to create a […]