Brief Overview of network: - Our network is pure level-3 level ISP backbone network. It is comprissed of mostly Cisco GSRs, 6500 & 7600 series devices. - IGP used in network is OSPF only and all the links used in backbone network are 10Gige & 1 Gige Ethernet only. - All edge and core routers in our network are receiving full internet routes through BGP but not redistributed in OSPF. - There are multiple leaf areas conneced to backbone area and each area is comprised of almost 10-25 devices. - There is huge database of OSPF and the timers used in OSPF are default.
Problem Description: - Few days back we faced link flap multiple times on one of our backbone router, which caused reconvergence of entire OSPF database. This convergernce took a long while because of huge OSPF database. - In order to achieve faster and stable convergence we are looking to fine tune OSPF timers using OSPF SPF/LSA throttling with default parameters.
Need suggestion, if it is recommended to implement OSPF SPF and LSA throttling in core backbone network of level-3 size ISP and what are the suggested values, which can be used when entire backbone is based on 1/10Gige ethernet links.
Changing OSPF Hello and Dead intervals using ip ospf hello-interval and ip ospf dead-interval commands respectively, from every OSPF-enabled interface is one option. The range is 1 - 65535. But considering that your network is very huge, sounds like a lot of work to me (which is okay if you are paid on hourly-basis ) since the values should match for each OSPF neighbor to form adjacency.
To me, the OSPF areas should be designed such that these triggered updates are not send across the whole network. If possible, try to design the network such that some areas are made STUB. Also, try to summarise at OSPF ABR router.
Yes I agree with Giuseppe regarding the spf-flooding command. I implemented something similar in a MPLS VPN network I helped build. We were using IS-S as the IGP inside the MPLS domain, and we tweaked SPF to minimum (spf-interval 1 1 1) to achieve sub-second convergence.
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