Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
38 Cards in this Set
- Front
- Back
What are the 4 most common uses for route-maps?
|
* Redistribution
* Policy-based routing (PBR) * NAT * BGP |
|
What is a big difference between a route-map and an access list?
|
route maps can modify the packet or route by using set commands
|
|
What happens if a route-map statement contain several match statements?
|
All match statements must be true for for the route-map statement to be considered matched. (A logical AND operation)
|
|
What is the purpose of policy based routing?
|
To let packets take a route other than the obvious shortest path.
|
|
What should be documented in an implementation plan when planning route map configuration for PBR?
|
* Define the route map, conditions to match, action when theres a match
* Which interface the route map will be attached to |
|
What should be documented in an implementation plan when planning route map configuration for redistribution?
|
* Define the route map, conditions to match, action when theres a match
* Define where the route map will be used to control redistribution |
|
What is the purpose of distribute lists?
|
To allow an access list to be applied to routing updates
|
|
Where is the distribute list configured?
|
Under the routing protocol process
|
|
What factors can distribute lists filter on?
|
* Incoming interface
* Outgoing interface * Redistribution from another routing protocol |
|
What should be documented in an implementation plan when planning to configure distribute lists?
|
* Define traffic filtering requirements that will be used to permit or deny routes, using an access list or a route map
* Define a distribute list to use the access list or route map, and wether it will be applied inbound or outbound |
|
What are the 3 steps to configure a distribute list?
|
* Identify the network addresses of the routes to filter and create an access list
* Determine if you want to filter traffic incoming or outgoing on an interface, or routes being distributed from another protocol * Use the distribute-list command to assign the access list to filter outgoing updates |
|
What are some drawbacks to using distribute lists as route filters?
|
* A subnet mask cannot be easily matched
* Access lists are evaluated sequentially for every IP prefix in the routing update * A extended access list can be cumbersome to configure |
|
What are some advantages of using prefix lists instead of access lists when doing route filtering?
|
Significant performance improvement over access lists in loadin and route lookup of large lists.
|
|
What are the key issues with redistribution?
|
* Routing feedback (loops)
* Incompatible routing information, path selection might not be optimal * Inconsistent convergence times |
|
What are the default seed metrics for these protocols?
RIP IGRP/EIGRP OSPF IS-IS BGP |
RIP 0, Infinity
IGRP/EIGRP 0, Infinity OSPF 20, 1 for BGP, all E2 (for OSPF to OSPF the metric is preserved) IS-IS 0, not infinity BGP BGP metric is set to IGP value |
|
Multipoint one-way only works well if:
|
- The receiving protocol supports different administrative distances for internal and external routes (EIGRP, OSPF, BGP)
- The AD of the receiving protocols external routers is higher than the AD of the "from"-protocols routes. |
|
How can you prevent loops in multipoint redistribution scenarios?
|
- Insert only internal routes from protocol A to B (and vice versa)
- Tag routes in redistribution points and filter based on these tags when configuring redistribution in the other direction. - Propagate metrics from routing protocol A to protocol B properly - Use default routes to avoid having to do two-way redistribution |
|
What is the safest way of implementing redistribution?
|
Only one direction on only one boundary router within the network.
(One-point one way) |
|
What are some common network performance issues related to routing?
|
* Excessive routing updates
* Presence of any route maps/filters * The number of routing protocols running in the same AS |
|
What are the solutions to common network performance issues related to routing?
|
* Design changes
* Using passive interfaces * Route filtering |
|
What techinques can be used to filter routes?
|
* Distribute lists
* Access lists * Route maps * Prefix lists |
|
What are some reasons for running more than one routing protocol?
|
* Migration
* Host system needs * Mixed-vendor environment * Political and geographical borders * MPLS VPNs |
|
What happens to the routing table of the router performing the redistribution?
|
Nothing, it doesnt change
|
|
What are some issues arising when redistributing routes?
|
* Routing loops
* Incompatible routing information * Inconsistent convergence times |
|
What are the two methods of one-point route redistribution?
|
one way and two way
|
|
What is a possible issue with one-point one way and one-point two way redistribution?
|
Suboptimal routing
|
|
What are the two methods of multipoint route redistribution?
|
One way and two way
|
|
What is a key issue with multipoint redistribution?
|
It is likely to introduce potential routing loops
|
|
In which routing protocol routing process can you use the "subnets" parameter when redistributing into that protocol?
|
OSPF
|
|
How can you prevent a routers routing updates from being sent through a specific router interface?
|
with the "passive-interface" router configuration command
|
|
How can the administrative distance be manipulated to influence the route selection process?
|
With the "distance" router configuration command for all protocols.
|
|
What two commands are good to use to verify route redistribution?
|
show ip route [ip address] and traceroute [ip address]
|
|
When configuring route-maps for PBR, which command goes under the interface?
|
ip policy route map [map-tag]
|
|
What can allow an access list to be applied to routing updates?
|
A distribute-list
|
|
What methods can be used to filter routes?
|
Access lists, route maps, distribute lists, prefix lists
|
|
What may be the cause of a routing loop in a network that has redundant paths between two routing processes?
|
Depending on how redistribution is deployed, routers might send routing information back into a routing protocol.
|
|
When configuring a default metric for redistributed routes, should the metric be set to a value larger or smaller than the largest metric within the receiving autonomous system?
|
Larger, to help prevent suboptimal routing and loops.
|
|
What are some applications of route-maps?
|
* Route filtering during redistribution
* PBR * NAT * BGP |