Genie's Tech Blog

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MPLS TE Affinity

Hello Friends, Today, i am going to have an interesting discussion on Coloring concept in MPLS TE which is actually implemented through Affinity value and mask. You must have already read in my previous posts as how MPLS TE works. Today, we will be seeing how Affinity works and what is it used for. Before we start off with Affinity, lets first discuss the MPLS TE property called Attribute-Flag. Its a 32-bit bitmap on a link that can indicate the existence of up to 32 separate properties on that link. The default value of this property is 0x0. The attributes can vary from 0x0 to 0xFFFFFFFF. Th... [More]

MPLS TE: Auto-Tunnel Mesh Groups

Hello Friends Today, I am going to discuss about one of the interesting features on MPLS TE which is the Auto-Tunnel feature which gives us the capability to create TE tunnels automatically based on the destination list. The Auto-Tunnel feature provides automatic creation of one-hop primary TE tunnels (Auto-Tunnel Primary), and both nhop and nnhop FRR backup TE tunnels (Auto-Tunnel Backup).  Auto-Tunnel Primary and Backup can be enabled separately via CLI configuration. The Auto-Tunnel Primary feature, once enabled, causes the router to dynamically create one-hop tunnels to directly... [More]

MPLS TE tunnels without IGP

Hello Friends, i was trying to test out few things on MPLS TE and then i came across an observation that you can build the MPLS TE tunnel without running an IGP (Interior Gateway Protocol). Later on, I made another observation that the MPLS TE tunnel would come up even if we don't have RSVP configured on the interfaces. Though both these tunnels and configurations totally defy the facts that we have read about MPLS Traffic-engineering and also defy the purpose of MPLS TE tunnels but still this stuff seems to be working out. Lets consider a sample topology say: R1 ---- R3 ---- R4 ---- R6 whe... [More]

Inter-Area MPLS TE on IOS-XR

Hello Everyone, As mentioned earlier, today I will be discussing about Inter-Area MPLS TE. In my previous blog, we already discussed regarding Inter-Domain MPLS traffic engineering and we further discussed on the Inter-AS MPLS traffic engineering. We are now going to the second form of Inter-Domain MPLS traffic engineering i.e. Inter-Area MPLS traffic engineering. Inter-Area MPLS TE is fairly simple as compared to Inter-AS MPLS TE. Also, I will be discussing this topic on IOS-XR platform. The MPLS TE Interarea Tunnels feature allows you to establish MPLS TE tunnels that span multiple Interio... [More]


Hello Everyone, Today I am going to discuss about Inter-AS MPLS Traffic-engineering (TE). Till now we have seen how MPLS behaves within a single AS but will not see the functionality and implementation of Traffic-engineering Tunels. Actually Inter-AS MPLS TE is a part of Inter-Domain Traffic-engineering in which a domain is identified as an IGP area or an Autonomous-System. In Inter-Domain TE, Head-End router lacks complete network topology to perform path computation in both cases.  Inter-Domain TE Fast-Reroute: The Inter-Domain TE FRR has the same configuration as the single doma... [More]

CSPF - The TE Algorithm

Hello Everyone, Today I thought of sharing with you some understanding on CSPF Algorithm. CSPF stands for Constraint Shortest Path First. This constraint-based routing is executed online by Ingress Router. The CSPF calculates an optimum explicit route (ER), based on specific constraints. The path is computed using traffic engineering database which takes the extensions of OSPF and IS-IS as input. The resulting route is then used by RSVP-TE. The CSPF in particular and any constraint based routing process requires following inputs: Bandwidth requirements Hop limitations Administr... [More]