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Posts Tagged ‘STP’

Cisco, HP ProCurve and MSTP

22/12/2010 Komentarze wyłączone

Not so far away and not so long ago we made a Plan: new, redundant LAN for small Data Center. In fact, it was boring work. Homogeneous equipment, star-like, flat topology: two redundant units to aggregate traffic, edge switches connected to both units to achieve redundancy and load-balancing by MSTP. Nothing special.

But Our Lady walks nearby and, in cloudy and windy morning, small, gold apple with engraved word „cheaper” flew through window in our office. After that we got: two HP 5400zl, bunch of HP 2910al, four Cisco 2960, stack of Cisco 2950… and unchanged requirements.

Then funny part of our work was to come. Fortunately MSTP in 2960s is compatible with one in 5400s. But these in 2950s… not. As expected and noticed in this document and here.

In fact, we were able to achieve something like „working” environment, but situation, when some switches in LAN don’t recognize root-switches (this mechanism is described in mentioned docs), was considered by us as unacceptable.

We thought…
we smoked…
we prayed to Eris…
and we made it!

It was so simple: maybe Cisco 2950 isn’t compatible with HP equipment – but it is compatible with 2960. So, we created second level in our spanning-tree and connected each 2950 to two 2960, instead to root-HP 5400s. Each 2960 is connected to two 5400s and, in this way, we got reliable network with fast-enough convergence. BPDUs sent and received from/by 2950s are translated by 2960s and all switches can see valid roots in MSTP regions.

Hail Eris! Sieg hail Discordia!

PS. Thanks to Kooba for corrections and advices.