show bgp ipv4 unicast summary
Displays a summary of BGP IPv4 unicast neighbor status, including prefixes received and state information.
Overview
The 'show bgp ipv4 unicast summary' command is a fundamental troubleshooting and monitoring tool for BGP on Cisco NX-OS (Nexus) switches. It provides a concise overview of all BGP IPv4 unicast peers, their session status, and the number of prefixes exchanged. This command is essential for network engineers to quickly assess the health of BGP peering relationships, verify that expected prefixes are being received, and identify any anomalies such as flapping sessions or missing routes.
BGP (Border Gateway Protocol) is the de facto inter-domain routing protocol used to exchange routing information between autonomous systems (AS). On Nexus switches, BGP is commonly used for data center interconnect, MPLS L3VPN, and Internet edge routing. The IPv4 unicast address family is the most common, carrying standard IPv4 routes. The summary output helps engineers confirm that BGP sessions are established (though the state is not explicitly shown in summary, the presence of uptime indicates an established session), that the BGP table version is incrementing, and that prefix counts are as expected.
In troubleshooting workflows, this command is often the first step. If a route is missing, checking the summary can reveal whether the neighbor is down, not advertising prefixes, or if the prefix count is lower than expected. It also helps in capacity planning by showing the number of prefixes received from each peer. On NX-OS, the command supports VRFs, allowing per-VRF BGP summaries in multi-tenant environments. The output format is slightly different from Cisco IOS, notably in the prefix statistics field which uses a slash-separated format indicating best, multipath, configured, suppressed, and advertised prefixes. Understanding this format is crucial for accurate interpretation.
show bgp ipv4 unicast summary [vrf vrf-name] [all] [neighbor ip-address]When to Use This Command
- Quickly verify BGP peering status and prefix counts after configuration changes.
- Troubleshoot BGP session flapping by checking state and uptime.
- Monitor memory usage and prefix limits for BGP neighbors.
- Audit BGP table size and identify neighbors with high prefix counts.
Parameters
| Parameter | Syntax | Description |
|---|---|---|
| vrf vrf-name | vrf vrf-name | Specifies the VRF for which to display BGP summary. If omitted, the default VRF is used. Useful in multi-VRF deployments. |
| all | all | Displays summary for all VRFs. Overrides any VRF specification. Provides a global view of BGP peers. |
| neighbor ip-address | neighbor ip-address | Limits output to a specific neighbor. Useful for focusing on a single peer's statistics. |
Command Examples
Basic BGP IPv4 Unicast Summary
show bgp ipv4 unicast summaryBGP summary information for VRF default, address family IPv4 Unicast BGP router identifier 10.1.1.1, local AS number 65001 BGP table version is 12345, IPv4 Unicast config peers: 3, capable peers: 3 10.0.0.1 4 65002 10 10 10 0 0 00:12:34 2/0/0/0 0/0/0/0 0 10.0.0.2 4 65003 10 10 10 0 0 00:11:22 5/0/0/0 0/0/0/0 0 10.0.0.3 4 65004 10 10 10 0 0 00:10:11 3/0/0/0 0/0/0/0 0
The output shows the BGP router ID, local AS, and table version. For each neighbor, it lists IP address, AS number, message statistics (sent/received), table version, prefix counts (best/multipath/configured/suppressed/advertised), and uptime.
Summary for a Specific VRF
show bgp ipv4 unicast summary vrf CUSTOMER_ABGP summary information for VRF CUSTOMER_A, address family IPv4 Unicast BGP router identifier 10.2.2.2, local AS number 65001 BGP table version is 5678, IPv4 Unicast config peers: 1, capable peers: 1 192.168.1.1 4 65005 5 5 5 0 0 00:05:00 10/0/0/0 0/0/0/0 0
This shows BGP summary for a specific VRF. The neighbor 192.168.1.1 is in AS 65005, with 5 messages sent/received, uptime 5 minutes, and 10 prefixes received.
Understanding the Output
The output begins with the VRF and address family context, followed by the BGP router ID and local AS number. The 'BGP table version' indicates the current version of the BGP table; increments signify changes. The line 'IPv4 Unicast config peers' shows the number of configured peers, while 'capable peers' shows those that have completed the TCP and BGP session establishment. For each neighbor, the fields are: Neighbor IP, AS number, BGP version (always 4), message statistics (sent/received), table version (sent to neighbor), input queue depth, output queue depth, uptime (HH:MM:SS), and prefix statistics. The prefix statistics are shown as a slash-separated string: best prefixes / multipath / configured / suppressed / advertised. Healthy values include uptime increasing, prefix counts stable, and no queue depth. Problem indicators: state not 'Established' (though not shown in summary), uptime resetting, or prefix counts dropping.
Configuration Scenarios
Basic BGP IPv4 Unicast Peering
Two Nexus switches in the same AS peering for iBGP.
Topology
Nexus-A (10.1.1.1) --- Nexus-B (10.1.1.2)Steps
- 1.Configure BGP on Nexus-A with AS 65001 and router-id 10.1.1.1.
- 2.Configure neighbor 10.1.1.2 remote-as 65001.
- 3.Activate IPv4 unicast address family.
- 4.Repeat on Nexus-B.
! Nexus-A
router bgp 65001
router-id 10.1.1.1
address-family ipv4 unicast
neighbor 10.1.1.2
remote-as 65001
address-family ipv4 unicastVerify: Use 'show bgp ipv4 unicast summary' to verify the neighbor is up and prefixes are exchanged.
Watch out: Ensure loopback interfaces are used for peering and that they are reachable via IGP.
BGP with VRF
Multi-VRF environment with separate BGP process per VRF.
Topology
Nexus (10.2.2.2) with VRF CUSTOMER_A and CUSTOMER_B.Steps
- 1.Create VRFs and assign interfaces.
- 2.Configure BGP with VRF instances.
- 3.Specify neighbors under each VRF.
! VRF CUSTOMER_A
vrf context CUSTOMER_A
rd 65001:100
router bgp 65001
vrf CUSTOMER_A
router-id 10.2.2.2
address-family ipv4 unicast
neighbor 192.168.1.1
remote-as 65005
address-family ipv4 unicastVerify: Use 'show bgp ipv4 unicast summary vrf CUSTOMER_A' to check peering.
Watch out: VRF BGP processes are independent; ensure correct VRF is specified.
Troubleshooting with This Command
When troubleshooting BGP issues on Nexus, start with 'show bgp ipv4 unicast summary'. If a neighbor is missing from the output, it may not be configured or the session may be down. Check the 'capable peers' count; if it's less than 'config peers', some sessions are not established. Use 'show bgp ipv4 unicast neighbors <ip>' for detailed state. If uptime is low or resetting, the session is flapping – check for MTU issues, TTL mismatches, or reachability problems. If prefix counts are zero or lower than expected, verify that the neighbor is advertising routes and that inbound prefix-lists are not filtering. The 'table version' should be consistent across neighbors; a large gap may indicate a slow convergence. Also, monitor memory usage with 'show bgp memory' if prefix counts are high. For VRFs, ensure you specify the correct VRF; otherwise, you may see an empty output. Use 'show bgp ipv4 unicast summary all' for a global view.
CCNA Exam Tips
Remember that 'show bgp ipv4 unicast summary' is the NX-OS equivalent of 'show ip bgp summary' on IOS.
Focus on the 'State/PfxRcd' column (not shown in summary but in detail) – in summary, check uptime and prefix counts.
Know that the 'table version' increments with each BGP update; a large gap between local and neighbor version may indicate a problem.
Common Mistakes
Confusing the prefix count format: NX-OS uses slash-separated fields (best/multipath/configured/suppressed/advertised) instead of a single number.
Forgetting to specify VRF when using VRFs; the command defaults to the default VRF.
Misinterpreting the 'capable peers' count as all configured peers; it only counts peers that have reached Established state.
Platform Notes
On Cisco NX-OS, the 'show bgp ipv4 unicast summary' command differs from Cisco IOS's 'show ip bgp summary' in several ways. The output includes a 'table version' field and the prefix statistics are displayed as a slash-separated string (e.g., '2/0/0/0/0') representing best/multipath/configured/suppressed/advertised prefixes. IOS uses a single 'PfxRcd' column. NX-OS also supports VRFs natively, requiring the 'vrf' keyword. The command is available in EXEC mode. Equivalent commands on other platforms: Juniper 'show bgp summary', Arista 'show bgp summary'. On older NX-OS versions, the command may be 'show bgp ipv4 unicast summary' without the 'vrf' option; always check the version.
Practice for the CCNA 200-301
Test your knowledge with hundreds of CCNA practice questions covering all exam domains.
Practice CCNA Questions