Wednesday, October 4, 2017

Cisco NX-OS/IOS Comparison Tech Notes

Cisco Nexus 7000 NX-OS/IOS Comparison Tech Notes

Cisco Nexus switches use the Cisco NX-OS Software. These comparisons are based on Cisco Nexus 7000 switches.

The following article compares default configuration differences between Cisco NX-OS Software and Cisco IOS Software.
  • Cisco NX-OS/IOS Software Default Configuration Differences
  • Catalyst 6500 IOS to NxOS Migration tool

The following articles compare Cisco NX-OS Software with Cisco IOS Software for common features:
  • Cisco NX-OS/IOS Configuration Fundamentals Comparison
  • Cisco NX-OS/IOS BGP (Basic) Comparison
  • Cisco NX-OS/IOS BGP (Advanced) Comparison
  • Cisco NX-OS/IOS DHCP Relay Comparison
  • Cisco NX-OS/IOS EIGRP Comparison
  • Cisco NX-OS/IOS HSRP Comparison
  • Cisco NX-OS/IOS Interface Comparison
  • Cisco NX-OS/IOS Layer-3 Virtualization Comparison
  • Cisco NX-OS/IOS Multicast Comparison
  • Cisco NX-OS/IOS Netflow Comparison
  • Cisco NX-OS/IOS OSPF Comparison
  • Cisco NX-OS/IOS Port-Channel Comparison
  • Cisco NX-OS/IOS SPAN Comparison
  • Cisco NX-OS/IOS STP Comparison
  • Cisco NX-OS/IOS TACACS+, RADIUS, and AAA Comparison

Cisco NX-OS/IOS BGP (Basic) Comparison

Objective
This tech note outlines the main differences in Border Gateway Protocol support between Cisco® NX-OS Software and Cisco IOS® Software. Sample configurations are included for the Cisco NX-OS and Cisco IOS Software for some common features to demonstrate the similarities and differences. Please refer to the NX-OS documentation on Cisco.com for a complete list of supported features.

BGP Overview
BGPv4 is a standard Exterior Routing Protocol defined in RFC 4271, commonly used to exchange network reachability information between autonomous systems. This document covers the features required for basic connectivity.

Important Cisco NX-OS and Cisco IOS Software Differences
In Cisco NX-OS:
  • BGP CLI configuration and verification commands are not available until you enable the BGP feature with the feature bgp command.
  • The BGP protocol requires an Enterprise Services license.
  • Autonomous system numbers can be configured as 16 or 32 bit values.
  • Address families need to be explicitly enabled (IE: IPv4 unicast, IPv6 unicast, etc…). All address families are disabled by default.
  • By default, eBGP supports 8 Equal Cost Paths and iBGP supports 1. The Cisco NX-OS supports up to 16 Equal Cost Paths for both eBGP and iBGP.
  • Automatic Route Summarization and Synchronization are disabled by default.
  • BGP consists of a hierarchical configuration based on neighbors and address families.
  • If a router ID is not manually configured, the loopback 0 IP address is always preferred. If loopback 0 does not exist, Cisco NX-OS selects the IP address for the first loopback interface in the configuration. If no loopback interfaces exist, Cisco NX-OS selects the IP address for the first physical interface in the configuration.
  • Neighbor logging is not enabled by default under the BGP instance. Neighbor logging can be enabled with the log-neighbor-changes command.
  • When neighbor authentication is configured, the BGP key is 3DES encrypted in the configuration. Cisco IOS Software requires the service password command to encrypt the password in the configuration.

Things You Should Know
The following list provides some additional facts about Cisco NX-OS that should be helpful when designing, configuring, and maintaining a BGP network.

  • One BGP instances can be configured per Virtual Device Context (VDC).
  • Numerous Virtual Route Forwarding (VRF) instances can be associated to a BGP instance.
  • If the feature bgp command is removed, all relevant BGP configuration information is also removed.
  • Network statements must be configured under their respective address-family configuration mode when advertising them via BGP.
  • The shutdown command under the BGP instance can be used to disable BGP while retaining the configuration.
  • The show running-config bgp command displays the current BGP configuration.
  • A BGP instance can be restarted with the restart bgp <instance #> command.
  • Graceful Restart (RFC 3623) is enabled by default.

Configuration Comparison
The following sample configuration code similarities and differences between the Cisco NX-OS and Cisco IOS Software CLIs. There are three significant differences: The Cisco NX-OS allows BGP to be enabled and disabled globally. It utilizes a hierarchical configuration that makes it easier to read. The Cisco NX-OS does not enable any address families by default. Each address-family needs to be explicitly enabled. The following examples demonstrate this using the IPv4 unicast address family.

Cisco IOS CLICisco NX-OS CLI
Enabling the BGP Feature
Cisco IOS Software does not have the functionality to enable or disable BGP.feature bgp
Configuring a BGP Instance and Router ID
router bgp 10
bgp router-id 192.168.1.1
router bgp 10
router-id 192.168.1.1
Configuring a BGP Neighbor (Internal)
router bgp 10
neighbor 192.168.2.1 remote-as 10
neighbor 192.168.2.1 update-source Loopback0
router bgp 10
neighbor 192.168.2.1 remote-as 10
update-source loopback0
address-family ipv4 unicast
Configuring a BGP Neighbor (External)
router bgp 10
neighbor 192.168.10.2 remote-as 11
router bgp 10
neighbor 192.168.10.2 remote-as 11
address-family ipv4 unicast
Advertising a Network in an Address Family (IPv4)
router bgp 10
network 159.142.1.0 mask 255.255.255.0
network 159.142.254.0 mask 255.255.255.0
neighbor 192.168.10.2 remote-as 11
router bgp 10
address-family ipv4 unicast
network 159.142.1.0/24
network 159.142.254.0/24
neighbor 192.168.10.2 remote-as 11
address-family ipv4 unicast
Configuring Neighbor Authentication (MD5)
router bgp 10
neighbor 192.168.10.2 remote-as 11
neighbor 192.168.10.2 password cisco123
router bgp 10
neighbor 192.168.10.2 remote-as 11
password 3 a667d47acc18ea6b
address-family ipv4 unicast
Configuring an Aggregate Address (Summary-Only)
router bgp 10
network 159.142.1.0 mask 255.255.255.0
network 159.142.254.0 mask 255.255.255.0
aggregate-address 159.142.0.0 255.255.0.0 summary-only
neighbor 192.168.10.2 remote-as 11
router bgp 10
address-family ipv4 unicast
network 159.142.1.0/24
network 159.142.254.0/24
aggregate-address 159.142.0.0/16 summary-only
neighbor 192.168.10.2 remote-as 11
address-family ipv4 unicast
Generating a Default Route for a Neighbor
router bgp 10
neighbor 192.168.10.2 remote-as 11
neighbor 192.168.10.2 default-originate
router bgp 10
neighbor 192.168.10.2 remote-as 11
address-family ipv4 unicast
default-originate


Verification Command Comparison
The following table compares some useful show commands for verifying and troubleshooting a BGP network configuration.

Cisco NX-OS BGPCisco IOS Software BGPCommand Description
show bgp convergence-Displays global convergence information
show bgp process-Displays global BGP process information
show bgp sessions-Displays information for all neighbors
show bgp statistics-Displays global BGP process statistics
---
show ip bgp <option>show ip bgpDisplays BGP Process and BGP table entries
show ip bgp x.x.x.xshow ip bgp x.x.x.xDisplays a specific network in the BGP table
show ip bgp x.x.x.x vrf-Displays a network in a specified VRF BGP table
show ip bgp x.x.x.x/lenshow ip bgp x.x.x.x maskDisplays a specific prefix in the BGP table
show ip bgp x.x.x.x/len longer-prefixshow ip bgp x.x.x.x mask longer-prefixDisplays a prefix in the table with longer prefixes
show ip bgp allshow ip bgp allDisplays the BGP table for all protocol families
show ip bgp community <word>show ip bgp community <#>Displays routes with a specific regular expression
show ip bgp community <aa:nn>-Displays routes with a specific community value
show ip bgp community internet-Displays BGP routes advertised to the Internet
show ip bgp community no-advertiseshow ip bgp community no-advertiseDisplays BGP routes not advertised to peers
show ip bgp community no-exportshow ip bgp community no-exportDisplays BGP routes not exported to next AS
show ip bgp community no-export-spoofed-Displays BGP routes not sent to outside local AS
show ip bgp community-list <name>show ip bgp community-list <name>Displays a specific BGP community list
show ip bgp dampening dampened-pathsshow ip bgp dampening dampened-pathsDisplays all Dampened paths
show ip bgp dampening flap-statisticsshow ip bgp dampening flap-statisticsDisplays flap statistics for BGP routes
show ip bgp dampening history-paths-Displays all history paths
show ip bgp dampening parametersshow ip bgp dampening parametersDisplays all of the Dampening parameters
show ip bgp extcommunity <word>-Displays routes with a specific regular expression for extended communities
show ip bgp extcommunity-list <name>-Displays a specific BGP extended community list
show ip bgp filter-listshow ip bgp filter-listDisplays all routes matching a specified filter list
show ip bgp flap-statistics-Displays all BGP route flap statistics
show ip bgp ipv4 multicast <option>show ip bgp ipv4 multicast <option>Displays BGP IPv4 multicast address families
show ip bgp ipv4 unicast <option>show ip bgp ipv4 unicast <option>Displays BGP IPv4 unicast address families
show ip bgp neighborsshow ip bgp neighborsDisplays detailed neighbor information
show ip bgp neighbors x.x.x.xshow ip bgp neighbors x.x.x.xDisplays detailed information for a neighbor
show ip bgp nexthop x.x.x.x-Displays all routes matching a specified next-hop
show ip bgp nexthop-database-Displays the next-hop database
show ip bgp pathsshow ip bgp pathsDisplays all BGP paths
show ip bgp peer-policy-Displays BGP peer policy by specified name
show ip bgp peer-session-Displays information about a peer session
show ip bgp peer-templateshow ip bgp unicast ipv4 templateDisplays information about a peer template
show ip bgp prefix-listshow ip bgp prefix-listDisplays routes matching a specified prefix-list
show ip bgp regexpshow ip bgp regexpDisplays routes matching a regular-expression
show ip bgp received-paths-Displays the paths stored for soft reconfiguration
show ip bgp route-mapshow ip bgp route-mapDisplays BGP routes matching a route-map
show ip bgp summaryshow ip bgp summaryDisplays a summary list of neighbors and statistics
show ip bgp vrfshow ip bgp vpnv4 vrfDisplays information for a specified BGP VRF

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