Using MLAG in Dell Networks A deployment guide for Dell Networking switches (version 1.
Revisions Date Description Author March, 2014 1.1 includes limitation of partner switches, added clarification of types of ports that can be used in peer-links, and changes to topologies supported in new appendix. Victor Teeter January, 2014 1.0 Initial Release Victor Teeter PAPER IS FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL INACCURACIES. THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND. © 2014 Dell Inc. All rights reserved.
Table of Contents Revisions ............................................................................................................................................................................................. 2 Executive Summary .......................................................................................................................................................................... 4 1 Introduction .....................................................................................
Executive Summary Multi-switch Link Aggregation or MLAG is a feature that allows two Dell Networking switches to act as a single switch, provides multiple paths across the network with benefits like: Failover in cases of failed cables or switches Increased bandwidth of up to double the bandwidth of a single switch Elimination of port blocking as well as reconvergence delays of spanning tree An MLAG domain is created by connecting a Dell Networking switch to another Dell Networking switch through Pee
1 Introduction MLAGs provide an active-active split aggregation deployment across two switches acting as one. MLAG creates a more resilient network with higher bandwidth capabilities. This white paper discusses MLAGs, how and when they are used, caveats to look out for, and instructions on how to implement MLAG into your network. Figure 1 below shows two very basic examples of MLAG domains.
2 Caveats for Enabling MLAG There are a few limitations in implementing MLAGs: Two identical switch models are required to create MLAG peers. This means an N2048 can only be peered with another N2048, an N3024 with another N3024, and so on. Peer devices must use the same expansion module type if ports from the expansion module are to be part of the MLAG interface. Neither of the two switches used as MLAG peers may be stacked with other switches.
Change any settings mentioned below on both the MLAG peers when required. Enable MLAG only after the above settings are configured on the two peer switches. It is also recommended for MLAG to be temporarily disabled in order to make subsequent changes to the above settings. Note: Be sure to schedule down time if making changes that impact traffic or cause data loss. Note: Failure to make these areas identical may cause sporadic traffic issues on the network which are difficult to troubleshoot.
3 Supported Topologies MLAG topologies contain several options. They can be a single layer (only one pair of MLAG peer switches) or two layers (two pair of MLAG peer switches). The peer-link between peers can have anywhere from 1 to 8 active interfaces to create the link. With these and other variables, there are dozens of ways to setup an MLAG. Table 2 lists all supported topology options.
4 Single-Tier Example This example shows the configuration of the two MLAG peers with two MLAG partners. The default spanning tree configuration is used and spanning tree is disabled on the peer link. Primary MLAG peer (27) (1/0/1) Peer-Link (48) N3048 Partner Switch A (47) MLAG Secondary MLAG peer (12) N3048 MLAG (29) (1/0/1) Partner Switch B (30) (28) Figure 4 (11) Single tier MLAG topology To configure the two MLAG peers in the basic configuration, follow the steps below: 1. 9 .
. Primary MLAG Peer (N3048) Secondary MLAG Peer N3048) switchport trunk native vlan 30 vpc 30 exit switchport trunk native vlan 30 vpc 30 exit interface port-channel 40 switchport mode trunk switchport trunk native vlan 30 vpc 40 exit interface port-channel 40 switchport mode trunk switchport trunk native vlan 30 vpc 40 exit Create a LAG (port-channel) for partner switch B to pass traffic interface gigabitethernet 1/0/47 channel-group 30 mode active description "MLAG-Partner-link" exit interfa
Note: Interfaces used to connect each peer to the partner switch LAG do not need to match on each peer. For instance, in the example above, one partner LAG interface connects to 1/0/47 on the primary peer while the other interface connects to 1/0/11 on the secondary peer. 2. Connect all cables as shown in Figure 4. 3. Run the show vpc brief command on either of the two MLAG peers to see which peer is the primary MLAG peer. 4.
Primary MLAG Peer Secondary MLAG Peer ----------Interface.............................................. Po40 Configured VLANs............................ 1,30 VPC interface state........................... Active ----------Interface............................................ Po40 Configured VLANs.......................... 1,30 VPC interface state.........................
5 Two-Tier Example Figure 5 shows a logical topology for a 2-tier fully meshed MLAG, offering full redundancy across all four MLAG peers. Six Dell N3024s are used for the example, however the same principals apply and the same commands can be used on the N2000 and N4000 series switches. A. 1 3 5 7 9 11 13 15 17 19 2 4 6 8 10 12 14 16 18 20 21 1 LNK 23 ACT 2 Stack No. LNK 22 ACT 24 COMBO P 1 SFP+ 2 = MLAG B.
In a full mesh, all eight ports joined together in the MLAG (four blue cables) are in the same port channel to achieve maximum redundancy. To configure the 2-tier in a full mesh configuration, follow the steps below: 1. Enter the commands below for each corresponding switch in the topology. 2. Cable the configuration as shown. 3. Enable MLAG (using the feature vpc command) on each switch. Similar commands are performed on all four MLAG peer switches.
. MLAG Peer B MLAG Peer C interface gigabitethernet 1/0/1 channel-group 40 mode active description "MLAG-Partner-Link" exit interface gigabitethernet 1/0/1 channel-group 40 mode active description "MLAG-Partner-Link" exit interface gigabitethernet 1/0/2 channel-group 40 mode active description "MLAG-Partner-Link" exit interface gigabitethernet 1/0/2 channel-group 40 mode active description "MLAG-Partner-Link" exit Assign interfaces to connect to partner D’s half of full mesh LAG interface gigab
MLAG Peer D MLAG Peer E description "MLAG-Partner-Link" exit description "MLAG-Partner-Link" exit Description of commands MLAG interface gigabitethernet 1/0/2 channel-group 40 mode active description "MLAG-Partner-Link" exit interface gigabitethernet 1/0/2 channel-group 40 mode active description "MLAG-Partner-Link" exit Assign interfaces to connect to partner C ‘s half of full mesh LAG interface gigabitethernet 1/0/14 channel-group 60 mode active switchport mode trunk switchport trunk allowed vla
Note: Interfaces used to connect each peer to the partner switch LAG do not need to match on each peer. For instance, in the example above, one partner LAG interface connects to 1/0/47 on the primary peer while the other interface connects to 1/0/11 on the secondary peer. Note: The partner switches must be configured with LAGs and connected to the MLAG peers, or the “Number of VPCs operational” in the show vpc brief command will show 0.
Local Members Status ----------------- -----Gi1/0/14 Up Local Members Status ----------------- -----Gi1/0/13 Up Peer Members ---------------Gi1/0/13 Peer Members Status ---------------- -----< * run command from Primary for this information > Status -----Up Note: Running the show vpc brief command on the primary shows the complete status of both peer switches. Running the show vpc brief command on the secondary shows status of the secondary only.
Appendix A.1 Unsupported Configurations Figure 7 shows examples of configurations that are not supported. The first topology shows an MLAG peer attempting to connect with a Dell VLTi peer. The second topology shows an MLAG peer attempting to connect with a Cisco vPC (or Cisco VSS) peer. Neither peer configurations shown in these scenarios are supported.
VLT is a feature similar to MLAG, but is available on the FTOS-based Dell Networking switches like the S4810. Each peer pair must use the same multi-chassis lag feature. This will provide the network with the same resiliency and improved bandwidth as when using MLAG in a multi-tier MLAG-only environment. A.3 Additional Resources Support.dell.com is focused on meeting your needs with proven services and support. DellTechCenter.
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