Can a router run BGP and IGP(ospf,eigrp,rip) at the same time

I wonder how routes get from on router to another within the same AS (IBGP) and between different ASes(EBGP).
Is neighbor command  the one that makes routes converge between IBGP and EBGP routers or we need to configure IGP (ospf.eigrp.rip) on each router in addition to BGP?

THANKS
jskfanAsked:
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Sandeep GuptaConnect With a Mentor ConsultantCommented:
what I wanted to know, whether is mandatory to have each router within BGP AS run a routing protocol ?

yes..you have to use some routing protocol.

If you are small in size then your can use static routing..you just need to redistribute those static routes in bgp.

router bgp <<as number>>
redistribute static
redistribute connected (if you have cascaded LAN)
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AkinsdConnect With a Mentor Network AdministratorCommented:
Yes, you need to configure additional route protocols (OSPF, EIGRP etc) with BGP.
BGP is really for internet connection or connection to ISPs.

1 rule concept in BGP synchronization is routes has to be learnt from other protocols before it is injected into IBGP (to prevent loops because IBGP can form neighbors with routers that are not directly connected)

You won't find any real network ever, that solely runs BGP. It is robust but very slow to converge.

Hope that helps
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Phyo HTET AUNGConnect With a Mentor Network Security AnalystCommented:
in bgp Best Path Selection Algorithm, bgp prefer eBGP over iBGP paths.
If you have two WAN router connecting to two difference ISP, you need to deploy ibgp. If you have one WAN router connecting to one ISP, you only need ebgp to ISP. ( it's also depend on ISP requirement ).

bgp used tcp connection to talk it's neighbor. In ibgp, to reach tcp connection from router-1 looppack ip address to router-2 loopback ip address, we need routing. ( static , eigrp, ospf or rip . etc. )

P.S : BGP best practice is identified itsef using it's loopback ip  address.

Hope this help.
Regards,
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Sandeep GuptaConnect With a Mentor ConsultantCommented:
remember BGP is not a routing protocol..for routing there should be any IGP.
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jskfanAuthor Commented:
if I understand:

1****Companies don't use BGP at all unless if they have 2 primary links to 2 different ISPs, in this case I believe ISPs engineers can configure BGP for the company.
IGP is supposed to be used by the company, unles if it is a small company and they use static routes . I don't think BGP works with static routes...Correct?

2**** between ISPs (Autonomous Systems), do they have to use IGP (ospf.eigrp.rip), in their routers, in order to get BGP routes carried between their routers?

I have seen some, video courses(CBTs) and they don't show that IGP is configured in each router inside BGP AS.

Thanks
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Phyo HTET AUNGConnect With a Mentor Network Security AnalystCommented:
1) BGP works with static route in same case, refer below link. For synchronization, bgp works with IGP not static route.

Link - 1
Link - 2

2) In my country we've tier 2 ISP and it' speaking only eBGP to tier 1 ISP. In case, we need to talk IGP for clean pipe for preventing DDoS attack.

Hope this help,
Regards
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jskfanAuthor Commented:
what I wanted to know, whether is mandatory to have each router within BGP AS run a routing protocol ?
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Phyo HTET AUNGConnect With a Mentor Network Security AnalystCommented:
what I wanted to know, whether is mandatory to have each router within BGP AS run a routing protocol ?


Depend on network design and network sizing, in my company, we used ebgp to tier 2 ISP. ibgp to difference WAN router with ospf.
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jskfanAuthor Commented:
Thank you
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