Category: Configuration

IPExpert CoD: MPLS-VPN

This post contains my notes from an old version of IPX Class on Demand by Joe Astorino.

RD has no special meaning—it is only used to make potentially overlapping IPv4 addresses globally unique

Route Targets are additional attributes attached to VPNv4 BGP routes to indicate VPN membership

Export Route Targets identifying VPN membership are appended to customer route when it is converted into VPNv4 route

RD & RT are extended BGP communities; neighbor send-community extended is required!

RR for VPNv4 does not need to be the same as RR of IPv4.

PE imposes 2 labels, the one if from LDP, and the bottom one is from VPNv4 address-family.

Each bgp address-family is a different RIB.

  • Import policy means that routes will come from the VPN extended community
  • Export policy means that routes will go to the VPN extended community

ARF –Automatic Route Filtering:  Only VPN information matching a locally configured RT will be imported
Could be disabled: no default bgproute-target filter

By default, when running OSPF over Frame-Relay and network type is anything except point-to-multipoint, on a spoke, the nexthop for a route originated  from another spoke will be that spoke.
But when the network type is point-to-multipoint, the nexthop will be the hub, and a host route for each spoke will exist.
So make sure to use point-to-multipoint when using MPLS.

RIP/EIGRP address-family version and summarization is different form the RIP/EIGRP’s itself.

When the customer needs the same AS on multiple sites, the AS Override feature should be triggered. So the PE will override its (prepend). Another way to handle this requirement is using allowas-in. Continue reading “IPExpert CoD: MPLS-VPN”

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IPExpert CoD: MPLS & LDP

This post contains my notes from an old version of IPX Class on Demand by Joe Astorino.

# hiding MPLS topology by just incrementing TTL 1 time when reaching the CE
router(config)# no ip mpls propagate-ttl

MPLS MTU is automatically decreased on LAN interfaces and increased on WAN interfaces.

Default mpls mtu is 1512 which supports 3 labels; MPLS MTU can be set by mpls mtu x

LDP router-id should be routable on network.

Connected routes are advertised as implicit-null label for PHP on upstream router

router(config)# mpls ldp neighbor ip labels accept acl
router(config)# mpls ldp tcp pak-priority //Kinda like setting QoS for LDP
!
#Like "ip accounting"
router(config-if)# mpls accounting experimental input/output
router(config-if)# mpls netflow egress
!
router# show mpls ldp binding // LIB
router# show mpls forwarding table // LFIB
router# show ip route // RIB
router# show ip cef ip detail //FIB

To clear LIB:

router(config)# no mpls ip
router(config)# mpls ip

PHP is the default.

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Default-route in EIGRP

I know it’s not such tricky thing, but to have in mind…

There are two solutions to originate 0.0.0.0/0 in EIGRP:

  1. (My preferred one) Static 0.0.0.0 0.0.0.0 pointing to an Interface (not next-hop) + network 0.0.0.0
    This way, there is no need of “auto-summary”, so you can use it switched off.
  2. Static 0.0.0.0 0.0.0.0 pointing to next-hop + “auto-summary” + “ip default-network“
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MPLS Fundamentals: 5 – MPLS-VPN

Most popular were Frame Relay or ATM technologies, providing VPN service at Layer 2. The provider had a Frame Relay or ATM backbone and supplied Layer 2 connectivity to the customer routers. This was commonly referred to as the  overlay model.

The service provider might have actually owned or managed the edge routers that were connected to the customer network. The point is that the routers were physically at the customer premises.

Peer-to-peer VPN networks existed, but they were not popular. The main reason is that they were not easy to deploy and maintain because they needed distribute lists, IP packet filters, or GRE tunnels. As explained in Chapter 1, MPLS VPN is an example of a highly scalable peer-to-peer VPN model.

The CE router does not peer with any of the CE routers from the other sites across the service provider network, as with the overlay model. The name  peer-to-peer model  is derived from the fact that the CE and PE form a peer at Layer 3.

Virtual routing/forwarding (VRF): is a VPN routing and forwarding instance. It is the name for the combination of the VPN routing table, the VRF Cisco Express Forwarding (CEF) table, and the associated IP routing protocols on the PE router.

A PE router holds the global IP routing table, but also a VRF routing table per VPN connected to the PE. Continue reading “MPLS Fundamentals: 5 – MPLS-VPN”

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GLBP Overview

In this post you’ll read some key points of GLBP and then I’ll invite you to test a sample implementation of GLBP.

GLBP means Gateway Load Balancing Protocol. What an easy definition 😀

It is a VGP (Virtual Gateway Protocol) / FHRP, similar to HSRP and VRRP. It’s one of the strongest kind of VGPs because it is capable of using multiple physical gateways at the same time.

This protocol attempts to overcome the limitations of existing redundant router protocols by adding basic load balancing functionality.

In addition to being able to set priorities on different gateway routers, GLBP allows a weighting parameter to be set. Based on this weighting (compared to others in the same virtual router group), ARP requests will be answered with MAC addresses pointing to different routers. Thus, load balancing is not based on traffic load, but rather on the number of hosts that will use each gateway router. By default GLBP load-balances in round-robin fashion.

GLBP elects one AVG (Active Virtual Gateway) for each group. Other group members act as backup in case of AVG failure. In case there are more than two members, the second best AVG is placed in the Standby state and all other members are placed in the Listening state. This is monitored using hello and holdtime timers, which are 3 and 10 seconds by default. The elected AVG then assigns a virtual MAC address for each member of the GLBP group, including itself, thus enabling AVFs (Active Virtual Forwarders). Each AVF assumes responsibility for forwarding packets sent to its virtual MAC address. There could be up to four active AVFs at the same time.

Continue reading “GLBP Overview”

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