In the previous post on MSS, MSS Clamping, PMTUD, and MTU, we learned how PMTUD is performed by setting the Don’t fragment flag in the IP header which leads to the device that needs to perform fragmentation dropping the packet
VRF Without Route Target – Will the Route Be Exported?
Yesterday I posted a tricky question to Twitter. If you have a working VPNv4 environment and create a VRF with only a Route Distinguisher (RD) but without Route Targets (RT), will the route be exported? The answer may surprise you!
CCDE – Carrier Supporting Carrier
Introduction In the previous post I showed some of the options to interconnect two AS so that a customer can buy a VPN in two different locations from two different SPs. There is another technology called Carrier Supporting Carrier or
CCDE – Inter AS L3 VPNs
Introduction Sometimes a customer needs a L3 VPN between two locations where the same SP is not present. This can be on a national or international basis. It would be possible to buy an Internet circuit and run an overlay
Unique RD per PE in MPLS VPN for Load Sharing and Faster Convergence
This post describes how load sharing and faster convergence in MPLS VPNs is possible by using an unique RD per VRF per PE. It assumes you are already familiar with MPLS but here is a quick recap. The Route Distinguisher
A Quick Look at MPLS-TE
Introduction I’m currently designing and implementing a large network which will run MPLS. This network will replace an old network that was mainly L2 based and did not run MPLS, only VRF lite. There are a few customers that need
Some pointers on OSPF as PE to CE protocol
There was a discussion at the Cisco Learning Network (CLN) about OSPF as PE to CE protocol. I wanted to provide some pointers on using OSPF as PE to CE protocol. RFC 4577 describes how to use OSPF as PE
Scaling PEs in MPLS VPN – Route Target Constraint (RTC)
Introduction In any decent sized service provider or even an enterprise network running MPLS VPN, it will most likely be using Route Reflectors (RR). As described in a previous post iBGP fully meshed does not really scale. By default all
MPLS troubleshooting scenario
I’m in final preparation for my second attempt and I have been doing a lot of troubleshooting scenarios lately. I created a MPLS topology in GNS3 and sent it to my friend Darren for testing. He is taking his lab
MPLS – notes
First defined in RFC 2547 Originally called tag switching and was Cisco proprietary MPLS is the open standard Operates at layer 2.5 between switching and routing Terms used in MPLS: LER = Label Edge Router – MPLS capable, placed at