S-Series: number of OSPF processes for 24 VRFs

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Hi,
S-Series S180, S140  support up to 256 VRF. We would need about 24 of them and want to use OSPF.
S-Series CLI guide states: "Multiple OSPF processes (process-id) are allowed per router. The S- K- and 7100-Series routers support 4 OSPF processes per VRF and 16 OSPF processes per router."

Does that mean we can use OSPF only in 16 VRFs? Or can one OSPF process be used for multiple VFRs?
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htw

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Posted 2 years ago

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Erik Auerswald, Embassador

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One OSPF process can be used in one VRF only.
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htw

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Hmm, then what can we do when we want to route in more than 16 VRFs? Use IS-IS? Does such an limit also exist for IS-IS?
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Erik Auerswald, Embassador

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Without looking at the data sheets, i.e. I do not know the actual limitations, I would suggest to look at BGP. Many BGP implementations, including EXOS, allow different VRFs in one routing process. You would need to check if this holds for EOS as well.

IS-IS has the same problem as OSPF, namely one link state database and SPF calculation per VRF. As such I would expect similar restrictions for IS-IS and OSPF. But again, I did not look at the data sheets.
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Erik Auerswald, Embassador

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Hi htw,

the documentation referenced in the original question is not intended to mean a limit of at most 16 OSPF processes per switch, I have learned recently.

I have tested that two SSA switches accept the creation of 17 (more than 16) OSPF processes in the default VRF. Adjacencies are formed and LSAs exchanged, the OSPF databases look fine. I have created 65 VRFs containing one OSPFv2 and one OSPFv3 process each on the same two SSAs, which work as well.

I have used SSA-T1068-0652 switches with EOS version 08.62.01.0035 for the above tests. This switch supports up to 256 VRFs, as shown by "show limits."

Using 24 VRFs with OSPF might work despite the stated limits in the CLI reference guide. You should consider a proof-of-concept with the hardware you intend to use.

Erik
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htw

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Hi Erik,
thanks for your test.

If we do a proof-of-concept and it works, wouldn't we still have the risk of emerging problems after s-series firmware updates as long as Extreme only supports and QAs up to 16 processes?

It would be interesting to know which factor is the reason for those 16 processes but only a extreme technician / code develoder can know this.
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Erik Auerswald, Embassador

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Hi htw,

I have been told by an Extreme employee that the number of "dynamic VRFs" specified in the release notes show what is supported. I did not receive an answer as to why the CLI reference contains specific limits that do not match the number of dynamic VRFs. :-(

Erik