Posts Tagged ‘VLT interconnect’

Dell Networking Extends Multipathing Capabilities with VLT Routing

Saturday, October 12th, 2013

Dell Networking recently released enhancements to their VLT multipathing technology in FTOS 9.2 now available on S4810, S4820T, and Z9000. For a quick primer on Dell’s VLT technology read my prior blog post here. The most noticeable enhancement is the support of layer 3 routing protocols over VLT. Additional enhancements include the ability of VLT peers to synchronize ARP entries learned from non-VLT interfaces, support for IPv6, and the ability to synchronize multicast routing tables between peer VLT ports. In this blog, I use 4 x Dell S4810s [FTOS 9.2] and 1 x Dell S60 (for a management switch) [FTOS 8.3.3.9] to demonstrate routed VLT.
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Twitt

Dell Force10 – Layer 2 Multipathing via Virtual Link Trunking (VLT)

Tuesday, December 18th, 2012

In this blog I use one Dell Force10 S50N [FTOS 8.4.2.7] and three Dell Force10 S4810 switches [FTOS 8.3.12.1] to demonstrate Dell Force10′s layer 2 mulipathing technology called Virtual Link Trunking (VLT). With VLT, you can create a LAG for a server, switch, or any device that supports LACP to two different upstream switches.

Traditionally, a LAG from an access switch or server could only connect to a single upstream switch. For redundanacy purposes, many users would implement stacking on the upstream switches and then use a port-channel/LAG up to the stacked switch now seen as one logical entity. However, stacking is not the preferred solution here. Two main reasons for this is that stacking provides a single control plane mechanism that is managed by the master switch; there is no hitless failover. Compare this to VLT which provides a dual control plane mechanism and is hitless in nature. Additionally, when upgrading the switch firmware, the entire stack would need to be brought down. With VLT, one switch can be upgraded at a time without bringing down the other switch.

Stacking is more seen at the ToR or access layer. The ToR switches are usually stacked and VLT is then used upstream to the aggregate and core switches. However, if the ToR switch supports VLT such as the S4810 does, VLT can also be used from the switch down to the server. 1 GbE switches like the Dell S50N and Dell S60 do not support VLT, so, in these cases, stacking can still be employed.

In the least recommended approach, if no VLT or stacking is used at the aggregate layer connecting to the ToR on a layer 2 network, spanning tree protocol (STP) would need to be employed to block redundant links. This would create link and switch level redundancy. The issue with this is that you lose half the ports/bandwidth on the switch. By leveraging VLT, you can have an active-active multi-path connection from an access server/switch to two upstream switches seen as one logical entity employing a dual control plane mechanism. No putting-up with STP or blocked ports! (more…)

Twitt