Part 1: BGP Lab Setup I. Topology
II) IP address Table
Lab3: BGP Route Filtering and Attribute Manipulation
Figure 1 – BGP Lab Topology
Router
IP Address of s2/0
IP Address of s2/1
IP Address of e0/0
IP Address of e0/1
Loopback 0
R1
176.1.1.1/24
–
10.1.1.1/24
10.1.1.0/24 Net1
–
R2
176.1.2.2/24
–
10.1.1.2/24
10.1.3.2/24
R3
10.1.4.3/24
–
–
10.1.3.3/24
10.1.2.3/24
10.1.2.0/24 (Net2)
R4
176.1.1.4/24
–
–
176.1.3.4/24
176.1.3.0/24 Net3
–
R5
176.1.2.5/24
176.1.4.5/24
–
176.1.3.5/24
–
R6
10.1.4.6/24
176.1.4.6/24
–
–
192.168.1.6/24
192.168.1.0/24 (Net4)
III) Configuration
1. Run EIGRP in AS100. EIGRP should carry all the routes in 10.1.0.0/16. 2. Setup BGP connections to the following router pairs.
R1-R2; R1-R3; R2-R3; R1-R4; R3-R6;
R4-R5; R5-R6;
router bgp
neighbor
Use additional neighbor ip-address next-hop-self command for the appropriate IBGP connections.
3. Use the network command in the routers to advertise networks 1, 2, 3 and 4 to their BGP peers. Do not use redistribution.
router bgp
network
example:
router bgp 45
network 192.1.1.0 255.255.255.0
4. Disable link R5-R2.
5. Configure no synchronization in all the BGP processes.
router bgp
Design 1: If you configure the routers correctly, they will learn all the routes. Record your configuration. (note: the network address of the serial links that are not required to learned by all the routers)
Part 2: Route Filtering
Objective: To study the usage of route filtering and route map. 1. Use the original network setup.
2. Use the distribute-list approach to perform the following filtering tasks:
• Routers in AS100 only advertise the networks from its own AS.
• R1 will not accept advertised routes to AS300 from its external BGP peer (R4).
• R3 will not accept advertised routes to AS200 from its external BGP peer (R6).
3. The filtering tasks above achieve the following routing results:
• AS100 uses link R3-R6 to reach Net4 and link R1-R4 to reach Net3.
• AS200 and AS300 will not use AS100 to reach each other.
4. To verify your configuration for the first result, examine the BGP table of R1 and R3. Both R1 and R3 should only have one route to Net 3 and one to Net4.
5. To test your configuration regarding the second result, disconnect link R6-R5. With the link disconnected, AS200 could not reach Net4 and AS300 could not reach Net3.
6. Repeat the above procedures using path-filtering and route-map approaches.
Design 1: Record your configurations for all three filtering approaches.
Part 3: Manipulation of BGP Attributes A) AS-PATH
Objective: To use AS_PATH attribute to control the path taken by the incoming external traffic.
1. Use the original network setup.
2. Configure the appropriate routers in AS100 to satisfy the following conditions:
• External traffic to Net1 uses R1.
• External traffic to Net2 uses R3.
Design 1: Use route map with as-path commands to configure the appropriate routers in AS100 to satisfy the above conditions. Note: Your configuration should allow R1 and R3 advertise both Net1 and Net2 to their peers.
Verify your configuration by examining the BGP tables and routing tables in R4 and R6.
3. Verify your configuration by examining the BGP tables and routing tables in R4 and R6.
B) Weight Attribute
Objective: To use weight attribute to select external routes.
4. Use the original network setup.
5. Configure the appropriate routers in AS100 to satisfy the following conditions:
• R1 chooses R4 to reach Net3 and Net4.
• R3 chooses R6 to reach Net3 and Net4.
6. Verify the configurations by examining the routing tables and BGP tables in R1 and R3.
C) Local-Preference Attribute
Objective: To use local-preference to select external routes.
1. Use the original network setup.
2. Configure the appropriate routers in AS100 to satisfy the following condition:
• AS100 chooses R4 to reach Net3 and Net4.
3. Enable the link between R2 and R5 and configure BGP connection between the two routers.
4. Clear the local-preference setup in step 2.
5. Configure the appropriate routers in AS100 to satisfy the following conditions:
• AS100 prefers R4 to reach Net4.
• AS100 prefers R6 to reach Net3.
D) Metric Attribute
Objective: To control external incoming traffic.
1. Use the network setup in part (C) step 3.
2. Configure the appropriate routers in AS100 to satisfy the following conditions:
• AS200 uses R1 to reach Net1.
• AS200 uses R2 to reach Net2.
Design 2: There are two possible command sets for the configurations. Namely, neighbor… weight… commands and route map commands. Configure the network using these command sets.
Note: Make sure that your configuration does not cause the routers to filter any routes advertised by their peers.
Design 3: Use bgp default local-preference command to configure the appropriate routers in AS100 to satisfy the above condition
Design 4: Use route map with set local-preference commands to configure the appropriate routers in AS100 to satisfy the above conditions.
Design 5: Use route map with set metric commands to configure the appropriate routers in AS100 to satisfy the above conditions
E) Community Attribute
Objectives: To prevent route propagation and perform attribute manipulation for a group of routes.
1. Use the original network setup with the following modification: Disable link between R3-R6.
2. Configure the appropriate routers in AS100 and AS200 to satisfy the following condition:
• Net1 is advertised to AS200 but not AS300.
• Net2 is advertised to both AS200 and AS300.
Design 6: Use set community command to configure the appropriate routers in AS100 to satisfy the above conditions
3. Enable the links R2-R5 and R3-R6. Configure BGP connections over these links.
4. Disable link R5-R6.
5. Configure the appropriate routers in AS100 and AS200 to satisfy the following condition:
• AS200 uses R1 to reach Net1 and Net2.
• AS200 uses R2 to reach Net4.
F) Peer Group
Objective: To use peer group commands to simplify BGP configuration.
1. Use the original network setup with the following modification:
• Enable link R2-R5 and configure a BGP connection over the link.
• Disable link R5-R6.
2. Configure the appropriate routers in AS100 to satisfy the following condition:
a) R3 does not advertise AS300 to R2 and R1.
b) R3 only accepts the route 176.1.3.0/24 from R1 and R2. It filters the other BGP advertisements from R1 and
R2.
Design 8: Use peer group commands to configure the appropriate routers in AS100 to satisfy the above conditions
Design 7: Configure one router in AS100 and another one in AS200 to satisfy the above conditions. Use community commands.
Q: Suppose you want AS200 preferring R1 to reach Net4 too, and you are only allowed to modify the configuration of a single router in AS100, discuss the most efficient way to achieve that.