[f-nsp] OSPF and BGP flapping when enabling a certain amount of BGP neighbors
Eldon Koyle
ekoyle+puck.nether.net at gmail.com
Fri Jun 22 13:50:52 EDT 2018
I'll second Dennis. Disabling icmp redirects is extremely important if you
have multiple addresses on a single interface.
If you have a lot of routes, you may need to change your system-max
values. Run 'show default values' and look for ip-route and ip-cache
values (and ipv6- equivalents). The defaults are usually quite low (290k
routes on our CER2024F's, this needs to fit your entire FIB). Change with
'system-max <parameter> <value>', write mem, then reload. On the MLX, you
also have to worry about cam partitioning profiles. The CER2024F may be
able to handle 1.5M routes in the BGP RIB, but it has a HW max of 524288 in
the FIB.
I have also seen a lot of lp-cpu usage caused by multicast traffic,
especially with older code.
If you see high lp cpu again in the future, you can run 'dm pstat' a few
times to try to get an idea of what kind of traffic you are receiving. The
first run is typically a throwaway, as it shows counts since the last run.
It gives per-PP stats, but I think the CERs only have one PP anyway. If
you are feeling brave, you can use 'rconsole' to connect to the LP and play
with 'debug packet capture' (captures/displays packets that are hitting the
lp cpu), but beware... I have had devices unexpectedly reboot playing with
that. Always specify a limit.
--
Eldon
On Fri, Jun 22, 2018 at 10:06 AM, Dennis op de Weegh <info at bitency.nl>
wrote:
> Can you post your confg?
>
> LP load looks high.
> Try to disable icmp redirect in config:
>
> no ip icmp redirect
>
> It's a Brocade thing...
>
>
>
> Kind regards/Met vriendelijke groet,
>
> Dennis op de Weegh
>
>
>
> Bitency
> Willem van Oranjestraat 9
> 4931NJ Geertruidenberg
>
> Kvk nummer: 20144338
> BTW nummer: NL213538519B01
>
> W: www.bitency.nl
> E: info at bitency.nl
> T: +31 (0)162 714066
>
>
> -----Oorspronkelijk bericht-----
> Van: foundry-nsp <foundry-nsp-bounces at puck.nether.net> Namens Frank Menzel
> Verzonden: vrijdag 22 juni 2018 17:57
> Aan: foundry-nsp at puck.nether.net
> Onderwerp: [f-nsp] OSPF and BGP flapping when enabling a certain amount of
> BGP neighbors
>
> Hi,
>
> one of our CER2024F routers started to behave weird without noticeable
> reason, we didn't apply any changes before:
>
> A while ago the device showed up in out monitoring with flapping OSPF
> sessions caused by malformed packets and BGP sessions with expired
> hold-timers. This made the device to become unresponsive, so we disabled
> most BGP sessions except the one to our transit partner and 4 iBPG
> sessions. This brought the device to an operational state again.
>
> In exchange we received a new identical device from our vendor and applied
> a configuration backup of the former device, but it behaves just like the
> old one when we took all sessions in service.
>
> To get an idea how many sessions are needed to cause issues we carefully
> took sessions of small networks in service one by one while observing cpu,
> memory usage and the number of routes installed. No issues occured, so we
> took two big sessions in service (DECIX route servers), again, nothing
> remarkable happened.
> Encouraged by that we simultaneously took 10 sessions in service and the
> ospf flapping started, so we disabled them and the device was able to cope
> with its workload again.
> To make sure we don't exceed the capabilities of the device we took those
> sessions in service one by one with a delay of 10 seconds, this did *not*
> cause OSPF flaps or BGP connections to restart, so we decided to take the
> last 10 remaining sessions in service at once again, which almost
> immediately caused OSPF flaps and BGP sessions to restart.
> Therefore we stopped all sessions we took in service before, except the
> transit partner and 4 iBGP sessions, but the flapping continued, the only
> way to get the CER to an operational state again was reloading it with most
> of the BGP sessions disabled by default.
>
> However, we were able to drag some information from the device during the
> last flapping, we didn't see a significant change in memory usage, but the
> load increased dramatically:
>
> SSH at CER(config-bgp)#sho cpu-utilization
>
> 00:09:57 GMT+01 Fri Jun 22 2018
>
> ... Usage average for all tasks in the last 1 seconds ...
> ==========================================================
> Name us/sec %
>
> idle 0 0
> con 35 0
> mon 190 0
> flash 44 0
> dbg 39 0
> boot 70 0
> main 0 0
> itc 0 0
> tmr 4358 0
> ip_rx 26720 2
> scp 54 0
> lpagent 357 0
> console 324 0
> vlan 0 0
> mac_mgr 199 0
> mrp 241 0
> vsrp 0 0
> erp 239 0
> mxrp 127 0
> snms 0 0
> rtm 638 0
> rtm6 301 0
> ip_tx 11100 1
> rip 0 0
> l2vpn 0 0
> mpls 0 0
> nht 0 0
> mpls_glue 0 0
> pcep 0 0
> bgp 212773 21
> bgp_io 240 0
> ospf 1005 0
> ospf_r_calc 1193 0
> isis 260 0
> isis_spf 0 0
> mcast 460 0
> msdp 23 0
> vrrp 0 0
> ripng 0 0
> ospf6 667 0
> ospf6_rt 0 0
> mcast6 557 0
> vrrp6 0 0
> bfd 20 0
> ipsec 57 0
> l4 0 0
> stp 0 0
> gvrp_mgr 0 0
> snmp 458 0
> rmon 25 0
> web 1573 0
> lacp 4199 0
> dot1x 0 0
> dot1ag 177 0
> loop_detect 127 0
> ccp 12 0
> cluster_mgr 131 0
> hw_access 0 0
> ntp 22 0
> openflow_ofm 15 0
> openflow_opm 30 0
> dhcp6 0 0
> sysmon 0 0
> ospf_msg_task 0 0
> ssl 0 0
> http_client 0 0
> lp 723566 76
> LP-I2C 35 0
> ssh_0 84 0
> ssh_1 2140 0
> ssh_2 5072 0
> ssh_3 43 0
>
> The documentation states the device is able to handle 1.5 Mio routes and
> we didn't get above this limit:
>
> SSH at CER(config-bgp)#show ip bgp route sum
> Total number of BGP routes (NLRIs) Installed : 1210135
> Distinct BGP destination networks : 697652
> Filtered bgp routes for soft reconfig : 394895
> Routes originated by this router : 4
> Routes selected as BEST routes : 410535
> BEST routes not installed in IP forwarding table : 0
> Unreachable routes (no IGP route for NEXTHOP) : 0
> IBGP routes selected as best routes : 79640
> EBGP routes selected as best routes : 330891
>
>
> SSH at CER(config-bgp)#show ip route sum
> IP Routing Table - 410845 entries
> 8 connected, 11 static, 0 RIP, 294 OSPF, 410532 BGP, 0 ISIS
> Number of prefixes:
> /0: 1 /4: 1 /8: 16 /9: 11 /10: 36 /11: 99 /12: 291 /13: 565 /14: 1099
> /15: 1924 /16: 13355 /17: 7910 /18: 13673 /19: 24926 /20: 38033 /21:
> 44870 /22: 86917 /23: 70274 /24: 106572 /25: 12 /26: 11 /27: 25 /28: 21
> /29: 21 /30: 67 /32: 115
> Nexthop Table Entry - 682 entries
>
> Can anybody give me some hint what could cause the behaviour described
> above or what to investigate to tackle that issue?
>
>
> --
> Frank Menzel - menzel at sipgate.de
>
> sipgate GmbH - Gladbacher Str. 74 - 40219 Düsseldorf
> HRB Düsseldorf 39841 - Geschäftsführer: Thilo Salmon, Tim Mois
> Steuernummer: 106/5724/7147, Umsatzsteuer-ID: DE219349391
>
> http://www.sipgate.de - http://www.sipgate.co.uk
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