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Ask the Expert: Configuring and Troubleshooting Border Gateway Protocol (BGP)

ciscomoderator
Community Manager
Community Manager

Welcome to this Cisco Support Community Ask the Expert conversation. This is an opportunity to learn and any ask questions about how to configure and troubleshoot Border Gateway Protocol with Cisco expert Vinit Jain.

Ask questions from Monday August 10th to Friday August 21, 2015

Border Gateway Protocol (BGP) is one of the most widely deployed protocols in networks today and is the definitive routing protocol in the Internet. BGP is a flexible protocol, in that a variety of options are available to network engineers. Furthermore, extensions and implementation enhancements make BGP a powerful and yet complex tool. Because of BGP's pervasive deployment across multiple networks and the large number of use-cases that BGP can be applied to, it is becoming increasingly important to understand how to troubleshoot BGP issues quickly and easily. I will be helping you answer your queries on how to troubleshoot BGP

 

Vinit will be helping you with all your queries on all of the above.

Vinit Jain presented at  Cisco Live in June 2015 on Troubleshooting BGP 
Click here for More Information

 

Vinit Jain, 3X CCIE #22854 is a Technical Lead in HTTS (High Touch Technical Support) team supporting customers in areas of routing, MPLS, TE, IPv6, multicast and a wide variety of platform issues like High CPU, Memory leak, etc IOS, IOS XE, IOS XR and NxOS code base. Has been delivering trainings within Cisco on various technology as well as platform troubleshooting topics. He has also written workbook on IOS XR fundamentals on Cisco Support Community. Vinit has CCIE in R&S, SP and Sec and holds multiple certifications on programming and databases.

Find other  https://supportforums.cisco.com/expert-corner/events.

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23 Replies 23

Hello Vinit,

Thank you for looking into this & verifying the behavior on a 7.2

These messages are printed by Netstack  & looks like, they are to be expected if the N7K has a BGP peer configured with MD5 password but the remote end doesn’t. Any connection attempts will be unsuccessful and will be droppedat the TCP layer. Since I dont see these logs  in a 5.1(6) code, appears to be an enhancement in the later codes.

 

Appreciate your help !!

 

Thanks

Suman

 

Jessica Deaken
Level 1
Level 1

Hello Vinit,

I need to know how much memory do I need to have in my router to receive the complete BGP table from my ISP? I could not find this information. 

Thank you for your response.

 

Hello Jessica

If I understand your question correctly, you are looking for information on memory requirement for Internet Routing Table on your router? I would say the memory requirement for the Internet Routing table would vary.The memory requirement is different on different platforms like you might require 4 Gig or 8 Gig or 16Gig DRAM with various options/features enabled (Single RP with SSO enabled or Dual RP or if the router is acting as RR) on ASR1k platform and it will also depend on the combination of RP with ESP card, or you might have to tweak the TCAM resources on 7600 platform (RSP720) to match the increased Internet Routing Table.

Please refer to the ASR1k platform data sheet as its highly used as Route Reflector in lot of network deployments:

http://www.cisco.com/c/en/us/products/collateral/routers/asr-1000-series-aggregation-services-routers/data_sheet_c78-441072.html

You can check the present status of the Internet Routing Table at the below website:

http://www.cidr-report.org/

But the proper answer to this question would depend on several other factors like:

 - What all services are you running on your router?

- Are you using soft-reconfiguration inbound?

- How many multiple paths do you have per prefix?

- What other services are you running on your router like L2VPN, L3VPN, etc?

- Are you also downloading IPv6 Table as well?

and various others. 

The memory requirement can be higher if you are also having IPv6 Routing table along with IPv4, then its much higher. 

There was a blog post on Cisco website when the Internet Routing table reached 512K milestone. You may want to refer that as well.

http://blogs.cisco.com/sp/global-internet-routing-table-reaches-512k-milestone

I would say based on the data sheet of the specific platform, you will have to choose the memory if you are planning to install the Internet Routing table.

Hope this helps.

 

Vinit

Thanks
--Vinit

Hello Vinit;

 

I have been searching information about MTBF. I would like to know if you can tell me How calculate the MTBF, I have the data sheets but I don´t know which datas I need (I mean what is the up time, down time and failures).

I need the MTBF of cgr-2010/k9, asa-5515-fpwr & c2921-cme-srst/k9.

 

Thank you. Have a nice day.

 

Bryan

Hello Bryan

Though this question outside the scope of the Ask the Expert discussion, I think you need to raise this question to the Cisco Partner / Cisco Project Manager from who helped you buy the product.

i have seen some data sheets where the MTBF value is documented but i couldn't find anything relevant for the above product id's. Thus, this query further needs to be raised with the respective engineering teams within Cisco to get you the relevant information.

Hope this helps.

Vinit

Thanks
--Vinit

fly
Level 2
Level 2

I know cpu generate traffic, IOS mark qos 6, such as bgp.

Can I remark bgp traffic which router cpu generated before traffic leave router's interface on platform such as rsp 720,LAN card?

Hello,

Not all packets generated by CPU are marked with CS6. Only routing protocol packets are marked with CS6 like OSPF, BGP, etc. If you perform a ping test from the router, the ICMP packet is generated by the CPU and is marked with a DSCP value of 0.

Yes, You can mark the traffic leaving the router (for example routing protocol packets). Here is a sample config below:

ip access-list extended test
 permit tcp any eq bgp any
 permit tcp any any eq bgp
!
class-map match-all test
 match access-group name test
policy-map test
 class test
  set ip dscp cs2
 class class-default
!
interface Ethernet0/0
 ip address 10.1.21.1 255.255.255.252
 ip ospf network point-to-point
 service-policy output test
!

This will mark the BGP packets as CS2. But note that its not a good practice to mark the routing protocol packets with a different DSCP value.

QoS policies needs to be designed properly else can cause drops in your network. 

Hope this answers your questions.

Regards

Vinit

Thanks
--Vinit

Hi,Vinit,

    Thank you!

    I try to persuade customer not to remark routing protocol and also try it in lab

Tom

Dean Weeks
Level 1
Level 1

My question is about iBPG path selection for default routes. My AS is multi-homed using two different eBGP gateways to my ISP. We can call my ISP facing gateways eBGP1 and eBGP2. I’m learning only the default route to the Internet over these gateways.

 

My iBGP routers (iBGP1 & iBGP2) are learning the default route from eBGP1 and eBGP2. To support an Active/Active multi-homed environment. I desire iBGP1 to forward to eBGP1 and iBGP2 to forward to eBGP2. Of course, eBGP2 is the backup gateway for iBGP1 and vice versa, eBGP1 is the backup for iBGP2.

 

The failover needs to be dynamic and occur timely, we know BGP doesn’t like change. How best could I achieve these goals? What are your ideas or best practices for this design.

 

 My idea is to use a filter lists on my iBGP routers. Where I increase the MED from prefixes (default route) I learn from my backup eBGP gateway.

 

Thanks

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