NET4009-Module 5a- Tshooting Conditional fwding redistribution

Conditional Matching

matching a route using access control lists and prefix lists

Two step process for defining a standard ACL

1. Define the ACL by using the command IP access-list standard {acl-number | acl-name}

2. Configure the specific ACE entry with the command [sequence] permit | deny source srouce-wildard

What makes extended ACLs for BGP different then regular

The source fields match against the network portion of the route, and the destination fieldsmatch against the network mask

Route maps

can filter networks much the same way as ACLs but they also provie additional capability through the addition or modification of network attributes

Four components of Route maps

• Sequence number

• Conditional matching criteria

• processing action

• optional action

Route map command

route-map route-map-name [permit | deny] [sequence-number]

Policy-Based Routing (PBR)

conditional forwarding of packets based on packetcharacteristics besides the destination IP address

PBR Characteristics

• Routing by protocol type (ICMP, TCP, UDP, and so on)
• Routing by source IP address, destination IP address, or both
• Manual assignment of different network paths to the same destination, based on tolerance, link speed or utilization

Drawbacks of PBR

• Administrative burden in scalability
• Lack of network intelligence
• Troubleshooting complexity

4 steps to configure PBR

1. Configure the route map

2. Identify the conditional match criteria

3. Use the command “set IP [default] next-hop ip-address [IP]

4. apply the route map to the inbound interface by using the interface parameter command IP policy route-map <route-map-name>

Sequential Protocol Redistribution

redistribution between multiple protocols over a series of routers

A route must exist in the RIB (routing table) of router doing redistribution in order for it to be redistributed into the destination protocol

True

EIGRP-to-EIGRP Redistribution Characteristic

• EIGRP autonomous systems preserves the path metrics during redistribution.

Destination Specific Behaviors: OSPF

• The seed metric is 1 for BGP-sourced routes and 20 for all other protocols.

• The exception is that if OSPF redistributes from another OSPF process, the path metric is transferred

The main differences between Type 1 and Type 2 External OSPF routes

• Type 1 routes are preferred over Type 2

• Type 1 metric equals the redistribution metric plus the total path metric

• Type 2 metric equals only the redistribution metric

Why is the OSPF process number locally significant for redistribution?

Allows linking the OSPF-enabled interfaces to a process

OSPF-to-OSPF Redistribution path metrics

Redistributing routes between OSPF processes preserves the path metric during redistribution, independent of the metric type