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New Member

BGP drives router CPU up and stay up

Dear All,

I am doing BGP with my upstream and my customers. One day after clearing BGP, my router CPU processing shoot up to 80%, when it is normally 20%, and stayed there. Also, the amount of memory usage also increased from 80Mb to about 120Mb.

Sometime, when I reset the BGP session, the CPU usage would goes down to about 40% but the memory usage would shoot up to 150Mb. But when the BGP session reset, the CPU would goes up while the memory would goes down.

Also, I just discovered that my router, a 7206 with 256MB of ram only have 180+mb recognized. The rest 70Mb is not. I wonder does it have something to do with the IOS that I am using. Right now I am using a 12.3(2)T.

Any assistance would be appreciated. Thanks.



Re: BGP drives router CPU up and stay up

I would say that not having enough memory would cause some issues, but I'm not certain that the BGP process should take 80% of the processor constantly because of it. Are the peers converging? It could be that your peers are constantly churning, so it never converges, and the BGP process is constantly sucking up processor time.

I don't know of any BGP bugs in this area in the code you are running.


New Member

Re: BGP drives router CPU up and stay up

Hi Russ,

Thanks for the reply.

But would not a 7206VXR with 256Mb of RAM be more than adequate to meet the need?

I am wondering would IOS be an issue because when I use an earlier version, I did not have the same issue but due to some features requirement, I need to upgrade the IOS.

Previously, when I am using 12.0, I can see 256Mb, but now, only 180Mb. I am wondering which IOS version should I be using so that I can get back my other 70Mb.

Another percularity that I am experiencing is that the table version is stuck at 0 for a few customers and their output queue is long, about 90+k.

If my peers are constantly churning and never converge, how can I go about resolving that problem.

Your assistance is much appreciated.



Re: BGP drives router CPU up and stay up

Could you post a show version and show region? The first couple of lines of show mem might also be useful, as well as a show ip route summary. It could be that your router was fine before because the image size of the earlier image was smaller.


New Member

Re: BGP drives router CPU up and stay up

Hi Russ,

Thanks for your assistance.

Here is the information as per your request.

Show verion:

Cisco Internetwork Operating System Software

IOS (tm) 7200 Software (C7200-IS-M), Version 12.3(2)T, RELEASE SOFTWARE (fc1)

Synched to technology version 12.3(1.9)

TAC Support:

Copyright (c) 1986-2003 by cisco Systems, Inc.

Compiled Fri 25-Jul-03 11:15 by ccai

Image text-base: 0x60008954, data-base: 0x61D4C000

ROM: System Bootstrap, Version 12.0(19990210:195103) [12.0XE 105], DEVELOPMENT SOFTWARE

BOOTLDR: 7200 Software (C7200-BOOT-M), Version 12.0(9)S, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1)

Poseidon uptime is 2 weeks, 4 days, 21 hours, 39 minutes

System returned to ROM by reload at 11:54:16 GMT Mon Nov 3 2003

Running default software

Last reload reason: Reload command

cisco 7206VXR (NPE300) processor (revision D) with 229376K/65536K bytes of memory.

Processor board ID 18282649

R7000 CPU at 262Mhz, Implementation 39, Rev 1.0, 256KB L2, 2048KB L3 Cache

6 slot VXR midplane, Version 2.0

Last reset from power-on

Bridging software.

X.25 software, Version 3.0.0.

PCI bus mb0_mb1 has 600 bandwidth points

PCI bus mb2 has 0 bandwidth points

3 FastEthernet/IEEE 802.3 interface(s)

16 Serial network interface(s)

125K bytes of non-volatile configuration memory.

46976K bytes of ATA PCMCIA card at slot 0 (Sector size 512 bytes).

63232K bytes of ATA PCMCIA card at slot 1 (Sector size 512 bytes).

4096K bytes of Flash internal SIMM (Sector size 256K).

Configuration register is 0x2102

Show region:

Region Manager:

Start End Size(b) Class Media Name

0x0E000000 0x0FFFFFFF 33554432 Iomem R/W iomem2

0x20000000 0x21FFFFFF 33554432 Iomem R/W iomem

0x5E000000 0x5FFFFFFF 33554432 Iomem R/W iomem2:(iomem2_cwt)

0x60000000 0x6DFFFFFF 234881024 Local R/W main

0x60008954 0x61D4AC63 30679824 IText R/O main:text

0x61D4C000 0x62E1891F 17615136 IData R/W main:data

0x62E18920 0x63303A1F 5157120 IBss R/W main:bss

0x63303A20 0x6DFFFFFF 181388768 Local R/W main:heap

0x70000000 0x71FFFFFF 33554432 Iomem R/W iomem:(iomem_cwt)

0x80000000 0x8DFFFFFF 234881024 Local R/W main:(main_k0)

0xA0000000 0xADFFFFFF 234881024 Local R/W main:(main_k1)

Show mem:

Head Total(b) Used(b) Free(b) Lowest(b) Largest(b)

Processor 63303A20 181388768 108860632 72528136 11416044 14765184

I/O 20000000 33554432 315252 33239180 33192616 33223004

I/O-2 E000000 33554432 3934776 29619656 29357200 29352892

Sh ip route sum:

IP routing table name is Default-IP-Routing-Table(0)

IP routing table maximum-paths is 16

Route Source Networks Subnets Overhead Memory (bytes)

connected 0 19 2548 2736

static 12 9 1512 3024

ospf 10 20 53 5256 10512

Intra-area: 21 Inter-area: 8 External-1: 0 External-2: 43

NSSA External-1: 0 NSSA External-2: 1

bgp 17927 89470 37810 9164228 18339540

External: 127280 Internal: 0 Local: 0

internal 1359 1581876

Total 90861 37891 9173544 19937688

I have actually increase the flash memory to 48mb and the IOS that I am using is c7200-is-mz.123-2.T which is only about 18Mb. Therefore, I believe it is adequate to meet the need.



Re: BGP drives router CPU up and stay up

> cisco 7206VXR (NPE300) processor (revision D) with 229376K/65536K bytes of memory.

This looks right, it's 256MB divided into I/O and main memory, minus some initialization memory (before IOS proper loads), which is fine. The next number of interest is this:

> Processor 63303A20 181388768 108860632 72528136 11416044 14765184

So, 181388768 is the total after IOS loads--you say the image size is 18MB, double that to account for decompression, and you have about 36MB. Figure the main region of memory, at 229376000-36000000, and you come out with about 19000000, which is close to what we show in the processor memory pool, so that's correct (there is some slop in here, a meg or two either way is pretty normal in a 256MB system, for loaders, conversions, rounding, block size restrictions, and other such stuff).

Now, we move on to fragmentation:

Free: 108860632 Largest: 14765184

Hmmm..... That's not so good, actually. Your largest free block is very big, plenty large enough, but you are seeing some fragmentation. I would expect the largest to be more on the order of at least 50% of the free, maybe even more like 80% of the free in normal operation, and you're down at the 15%, perhaps, of the free memory range. The lowest is also pretty low, probably from memory usage shooting up as you've described.

Now, the question is, are these signs of memory issues a cause or a symptom? My guess is they are a symptom, rather than a cause, in this case. That's because you aren't seeing the problems consistently, and it makes sense that the high memory util is leading the fragmentation.

But, it's also coupled with high CPU utilization, especially just after a BGP session reset. This indicates some issue with the BGP session reset, probably. I know there were, actually, some bugs in this area recently, though I can't put my finger on the defect number or where the fixes were committed.

My suggestion (now you'll be able to guess that I'm an old TAC hand): take one upgrade, and one reload, and call me in the morning.... Seriously, though, that this happens when you are resetting the BGP peers is definitely symptomatic of the bug I'm thinking about, and the IOS version you're in is just about right for it, along with the version you upgraded from.



New Member

Re: BGP drives router CPU up and stay up

Dear Russ,

Thanks for the reply.

But I don't get what you mean about "take one upgrade, and one reload". Though I do understand about calling you in the morning. Can I have you contact number? :-)

Seriously, are you suggesting that all I need to do is to reload my router and upgrade the IOS? So which IOS should I upgrade to?

Really appreciate all the help you rendered.



Re: BGP drives router CPU up and stay up

Well, you're already running 12.3T. I would either go to the latest 12.2T, or to the later 12.3T. As for contact information, no... I left the TAC about 4 years ago!



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