Route Summarization

This chapter contains the following sections:

Route Summarization

Route summarization simplifies route tables by replacing many specific addresses with an single address. For example, 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 can be replaced with 10.1.0.0/16. Route summarization policies enable routes to be shared efficiently among border leaf switches and their neighboring leaf switches. BGP, OSPF, or EIGRP route summarization policies are applied to a bridge domain or transit subnet. For OSPF, inter-area and external route summarization are supported. Summary routes are exported; they are not advertised within the fabric.

Guidelines and Limitations

A route summarization policy configured under an external EPG will result in the summarized prefix being advertised to all of the BGP peers that are connected to the same border leaf switch and in the same VRF. This includes BGP peers that belong to different L3Outs if the same border leaf switch and VRF condition is met.

If you do not want this behavior to take place and you want to limit which BGP peers receive the aggregate route, block the routes where applicable using outbound route-maps on the respective L3Outs.

Configuring Route Summarization for BGP, OSPF, and EIGRP Using the GUI

Before you begin

For each of the following configurations, you have already created an L3 Out. For the L3 Out, you can create external routed networks, subnets, and route summarization polices.

Procedure

Step 1

Configure BGP route summarization using the GUI as follows:

  1. On the menu bar, choose Tenants > common

  2. In the Navigation pane, expand Networking > L3Outs .

  3. Right-click on L3Outs, then select Create L3Out.

    The Create L3Out wizard appears.

  4. In the work pane, enter the necessary information (Name, VRF, and L3 Domain), then check the check box next to BGP.

  5. Click Next.

    The Nodes and Interfaces window appears.

  6. In the Nodes and Interfaces window, fill in the appropriate fields, then click Next.

    The Protocols window appears.

  7. In the Protocols window, fill in the appropriate fields, then click Next.

    The External EPG window appears.

  8. Enter a name in the Name field, then uncheck the Default EPG for all external networks field.

    The Subnets field appears.

  9. Click + above Route Summarization Policy.

    The Create Subnet dialog box appears.

  10. In the Specify the Subnet dialog box, you can associate a route summarization policy to the subnet as follows:

Example:

  • Enter an IP address in the IP Address field.

  • Check the check box next to Export Route Control Subnet.

  • Check the check box next to External Subnets for the External EPG.

  • From the BGP Route Summarization Policy drop-down menu, select either default for an existing (default) policy or Create BGP route summarization policy to create a new policy.

  • If you selected Create BGP route summarization policy, the Create BGP Route Summarization Policy dialog box appears. Enter a name for it in the Name field, check the Control State check box for Generate AS-SET information, click Submit, click OK, the click Finish.

Step 2

Configure OSPF inter-area and external summarization using the GUI as follows:

  1. On the menu bar, choose Tenants > common.

  2. In the Navigation pane, expand Networking > L3Outs > External EPGs, then click on the configured external EPG.

    The overview information for that configured external EPG appears.

  3. In the work pane, click the + sign above Route Summarization Policy.

    The Create Subnet dialog box appears.

  4. In the Specify the Subnet dialog box, you can associate a route summarization policy to the subnet as follows:

Example:

  • Enter an IP address in the IP Address field.

  • Check the check box next to Export Route Control Subnet.

  • Check the check box next to External Subnets for the External EPG.

  • From the OSPF Route Summarization Policy drop-down menu, choose either default for an existing (default) policy or Create OSPF route summarization policy to create a new policy.

  • If you chose Create OSPF route summarization policy, the Create OSPF Route Summarization Policy dialog box appears. Enter a name for it in the Name field, check the check box next to Inter-Area Enabled, enter a value next to Cost, click SUBMIT.

Step 3

Configure EIGRP summarization using the GUI as follows:

  1. On the menu bar, choose Tenants > common

  2. In the Navigation pane, expand Networking.> L3Outs.

  3. Right-click on L3Outs, choose Create L3Out.

    The Create L3Out dialog box appears.

  4. In the work pane, check the check box next to EIGRP.

  5. Enter a name in the Name field, click NEXT.

    The External EPG Networks dialog box appears.

  6. In the work pane, click the + sign.

    The Define an External Network dialog box appears.

  7. Enter a name in the Name field, then click the + sign above Route Summarization Policy.

    The Create Subnet dialog box appears.

  8. In the Specify the Subnet dialog box, you can associate a route summarization policy to the subnet as follows:

Example:

  • Enter an IP address in the IP Address field.

  • Check the check box next to Export Route Control Subnet.

  • Check the check box next to External Subnets for the External EPG.

  • Check the check box next to EIGRP Route Summarization, click OK, click OK, click FINISH.