EVPN Type 4 (Ethernet Segment route) Explained

Ethernet Segment Routes are needed in multi-homing scenario and used for Designated Forwarder Election. Designated Forwarder is responsible for sending broadcast, unknown multicast and multicast (BUM) traffic to the CE on a particular Ethernet Segment.

RFC 7432 allows selecting a DF at the granularity of <ES, VLAN> for VLAN-based service and <ES, VLAN bundle> for VLAN-aware service. This enables load-balancing of BUM traffic at a VLAN or VLAN-bundle level.

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EVPN Type 3 (Inclusive Multicast Ethernet Tag route) Explained

Type 3 routes are required for Broadcast, Unknown Unicast and Multicast (BUM) traffic delivery across EVPN networks. Type 3 advertisements provide information about P-tunnels that should be used to send BUM traffic.

Without Type 3 advertisements, ingress router would not know how to deliver BUM traffic to other PE devices that comprise given EVPN instance.

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EVPN Type 2 (MAC/IP Advertisement route) Explained

Type 2 routes are used to advertise MAC addresses and IP addresses that might be associated with aforementioned MAC addresses.

In order to advertise Type 2 routes, PE needs to learn MAC addresses from the directly attached CEs. This is done via normal data-plane learning mechanisms. RFC 7432 also allows for MAC address learning via control plane interaction between PE and CE, although we have not see this implemented by any vendors.

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EVPN Type 1 (Ethernet Auto-Discovery) Explained

Type 1 advertisements are used for two distinct functions – Fast Convergence and Aliasing. EVPN Fast Convergence allows PE devices to change the next-hop adjacencies for all MAC addresses associated with a particular Ethernet Segment. EVPN aliasing allows traffic to be balanced across multiple egress points.

Type 1 routes are only advertised if Ethernet Segment Identifier is set to non-zero value, meaning that Type 1 routes are only originate for multi-homed sites.

Please refer to the following cheatsheet if you are not familiar with EVPN Terminology.

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EVPN Terminology Reference (RFC 7432, etc)

  • AC, A-C: Attachment Circuit
  • AD, A-D: Ethernet Auto-Discovery route
  • Ethernet Segment (ES): When a customer site (device or network) is connected to one or more PEs via a set of Ethernet links, then that set of links is referred to as an ‘Ethernet segment’.
  • Ethernet Segment Identifier (ESI): A unique non-zero identifier that identifies an Ethernet segment is called an ‘Ethernet Segment Identifier’. ESI 0 denotes a single-homed site.  ESI {0xFF} (repeated 10 times) is known as MAX-ESI.
  • Ethernet Tag: An Ethernet tag identifies a particular broadcast domain, e.g., a VLAN. An EVPN instance consists of one or more broadcast domains.
  • Ethernet Tag ID: 32-bit field containing either a 12-bit or 24-bit identifier that identifies a particular broadcast domain (e.g., a VLAN) in an EVPN instance.
  • EVI: An EVPN Instance spanning the Provider Edge (PE) devices participating in that EVPN.
  • EVPN: Ethernet Virtual Private Network.
  • IPL: IP address length
  • IRB: Integrated Routing and Bridging interface
  • NVE: Network Virtualization Edge
  • MAC-VRF: A Virtual Routing and Forwarding table for Media Access Control (MAC) addresses on a PE.
  • MAX-ET: Reserved Ethernet Tag ID {0xFFFFFFFF} is known as MAX-ET
  • MAX-ESI: Reserved ESI {0xFFFFFFFFFFFFFFFFFFFF} is known as MAX-ESI
  • ML: MAC address length
  • TS: Tenant System
  • VA: Virtual Appliance

BGP Next-Hop Self Explained

One of the common questions asked by people who begin their BGP journey is related to BGP ‘Next-Hop Self’ configuration option. What does it do? Should I use it on my network? What will happen if I forget to configure it? Today we’ll try to answer these questions.
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BGP Looking Glass

Brief introduction into Public BGP Looking Glass servers and how to use them to troubleshoot real-life issues. 

One of the most common tasks performed by BGP administrator is troubleshooting of prefix propagation over the Internet. You might have originated a prefix advertisement from within your Autonomous System, but was this prefix accepted by your Upstream Peers? If it was, did your Transit peers propagate this information to the global Internet, or did the prefix get lost or summarized somewhere within their networks because you might set a wrong community? Is it possible that your prefix has been hijacked by somebody else?
Public Looks Glass (LG) and Router-Servers (RS) allow you to get an answer to these questions in a matter of seconds.
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Cisco / Juniper Troubleshooting Commands

 About This Document

This document provides a cheat sheet of commonly used troubleshooting commands used in Cisco and Juniper environments. The list is incomplete. Please send us a note if you want to contribute.

Management

Cisco IOS Juniper JunOS Description
show tech-support request support info
request support information | save /var/tmp/RSI.txt
file archive compress source RSI.txt destination RSI.txt.tgz
Gather support info for vendor’s TAC
show hardware show chassis hardware Show hardware-related info
show version show system uptime Show system’s uptime
show processes cpu
show processes cpu sorted
show processes cpu history
show chassis routing-engine
show system processes extensive
show system threads
Verify CPU Utilization
show processes memory
show memory summary
show system processes extensive
show task memory detail
Verify Memory Utilization
dir bootflash: show system core-dumps Check for crash files / core dumps
dir file list Show directory structure
show system storage Verify available storage space
show users show system users List connected users
clear line X request system logout user ABC Disconnect user
start shell Enter Unix Shell
monitor traffic interface ge-0/0/1 Monitor traffic on the interface (will not show transit packets)
monitor traffic interface ge-0/0/1 write-file test.pcap Write control pacets into pcap file
show snmp mib walk .1.3.6.1.4.1.2636.3 Walk SNMP OID directly on a router
request system software rollback Request to the previous software version

L3 Routing

Static, Connected Routes and Routing Table

Cisco IOS Juniper JunOS Description
show ip route show route Show routing table
show ip cef show route forwarding-table Show forwarding table
show ip route connected show route protocol direct Show directly connected (attached) routes
show ip route static show route protocol static Show static routes
show route hidden Show hidden routes. Invalid route, e.g. route with unreachable next-hop will be marked as hidden

BGP

Cisco IOS Juniper JunOS Description
show ip bgp summary show bgp summary Show summary view of BGP neighbors
show ip bgp neighbor A.A.A.A advertised show route advertising-protocol bgp A.A.A.A Check routes advertised towards a peer
show ip bgp neighbor A.A.A.A received show route receive-protocol bgp A.A.A.A Check routes received from a peer
show ip bgp show route protocol bgp Check BGP routes

IS-IS

IOS IOS-XR JunOS Description
show clns interface show isis interface show isis interface Show IS-IS enabled interfaces
show clns neighbors show isis adjacency show isis adjacency Show protocol adjacencies
show clns traffic show isis statistics show isis statistics IS-IS statistics
show isis database show isis database show isis database Brief Database Information
show isis database verbose show isis database verbose show isis database extensive Detailed Database Information
show ip route isis show route isis show route protocol isis IS-IS learned routes
  show isis adjacency-log

 

show isis error-log

   IS-IS historical information