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Routing Protocols Question

KraftDinner

Sorry for posting so much here but I really want to wrap my head around networking and google can't always answer my questions in depth,

 

So I'm a bit foggy on what routing protocols actually do and how they're set up. I know that they establish the best route for a network but is that all? Also, is a routing protocol assigned to a network by the sys admin, and could there be more than one routing protocol per network?

 

Any help is appreciated, thank you!

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In the simplest of terms, a router "routes" packets between two networks. 

 

You home firewall is a router. It routes traffic between your local 192.168.x.x network and the WAN IP your ISP has given you. Typically a system has a "default gateway" or route they are assigned, so if they cannot find anything locally, the send the request off to the router to sort out. It then either has the path to find where you need to go stored local (cached, static assigned, etc.) and routes your traffic, or it can use it's defined default gateway to pass your request down the line to find a suitable path, and so on...

 

There are a bunch of routing protocols. This page from Cisco gives a really good overview:

http://www.cisco.com/c/en/us/td/docs/net_mgmt/active_network_abstraction/3-7/reference/guide/ANARefGuide37/routpro.html

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Follow me on Twitter for updates @Whaler_99

 

 

 

 

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In the simplest of terms, a router "routes" packets between two networks. 

 

You home firewall is a router. It routes traffic between your local 192.168.x.x network and the WAN IP your ISP has given you. Typically a system has a "default gateway" or route they are assigned, so if they cannot find anything locally, the send the request off to the router to sort out. It then either has the path to find where you need to go stored local (cached, static assigned, etc.) and routes your traffic, or it can use it's defined default gateway to pass your request down the line to find a suitable path, and so on...

 

There are a bunch of routing protocols. This page from Cisco gives a really good overview:

http://www.cisco.com/c/en/us/td/docs/net_mgmt/active_network_abstraction/3-7/reference/guide/ANARefGuide37/routpro.html

Thanks a lot, I guess my only other question regarding routing protocols is, is there a specific routing protocol that will be assigned to a network? For example say you assign EIGRP to your network, will it only use that protocol?

 

EDIT: I guess EIGRP would only be able to route between the same network, to different subnets since it's an internal protocol right?

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Typically higher end devices can support multiple routing protocols and is usually based on what your core router is running. But, you would pick and only run the one protocol on it. Cisco routers for instant can do EIGRP, OSPF and hey, could even do RIP if you you wanted to. :) But you would pick one and enable it.

A large private LAN/WAN could be all EIGRP if you have all Cisco, and that would work very well. In large, corporate networks they typically will have one routing protocol running. The Internet though has a few, based on various devices. Typically the routing protocol is just how the device builds and figures out the best way to route your traffic. So, your main router, running EIGRP doesn't know what to do. So, it passes the traffic to it's next hop, a router that might be using OSPF to build its database and route. The large core routers and most at large ISP and data centers are using BGP. 

 

Most home LAN's are not running a routing protocol but are a switched (layer 2) network to find all your local stuff and you are then all traffic for the internet is routed out...

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Follow me on Twitter for updates @Whaler_99

 

 

 

 

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Typically higher end devices can support multiple routing protocols and is usually based on what your core router is running. But, you would pick and only run the one protocol on it. Cisco routers for instant can do EIGRP, OSPF and hey, could even do RIP if you you wanted to. :) But you would pick one and enable it.

A large private LAN/WAN could be all EIGRP if you have all Cisco, and that would work very well. In large, corporate networks they typically will have one routing protocol running. The Internet though has a few, based on various devices. Typically the routing protocol is just how the device builds and figures out the best way to route your traffic. So, your main router, running EIGRP doesn't know what to do. So, it passes the traffic to it's next hop, a router that might be using OSPF to build its database and route. The large core routers and most at large ISP and data centers are using BGP. 

 

Most home LAN's are not running a routing protocol but are a switched (layer 2) network to find all your local stuff and you are then all traffic for the internet is routed out...

Awesome thanks so much! :) this really summarized everything for me 

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Awesome thanks so much! :) this really summarized everything for me 

 

You can spend a lifetime reading up on this stuff. One thing to remember, if you are at a site like Cisco, which has tons of great info, be careful not to drink to much of the Kool-aid. They love they proprietary protocols. :) But that seems to be lessening more and more.

Forum Links - Community Standards, Privacy Policy, FAQ, Features Suggestions, Bug and Issues.

Folding/Boinc Info - Check out the Folding and Boinc Section, read the Folding Install thread and the Folding FAQ. Info on Boinc is here. Don't forget to join team 223518. Check out other users Folding Rigs for ideas. Don't forget to follow the @LTTCompute for updates and other random posts about the various teams.

Follow me on Twitter for updates @Whaler_99

 

 

 

 

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You can spend a lifetime reading up on this stuff. One thing to remember, if you are at a site like Cisco, which has tons of great info, be careful not to drink to much of the Kool-aid. They love they proprietary protocols. :) But that seems to be lessening more and more.

Haha, i'm currently studying for the Net+ and the book I'm reading is super dry. I can't take it anymore ;( 

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Larger networks would operate with more than one routing protocol. The internal network routing on local sites would be using for example OSPF but use BGP on the border routers between sites. This is where route redistribution and summarization/aggregation topics start coming in to play.

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Larger networks would operate with more than one routing protocol. The internal network routing on local sites would be using for example OSPF but use BGP on the border routers between sites. This is where route redistribution and summarization/aggregation topics start coming in to play.

Yeah I was reading up on this, BGP is typically used in large corporations to link multiple internal networks as well therefore making it a somewhat hybrid protocol since it can technically be used as an IGP as well as an EGP.

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Have a read of this, http://www.enterprisenetworkingplanet.com/netsp/article.php/3617346/Networking-101--Understanding-iBGP.htm

 

The network where I work is kinda of different than usual, its all BGP. Not your typical setup. We do have 3 datacenters (2 really, 1 is tiny) with DR replication/failover between them etc.

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Have a read of this, http://www.enterprisenetworkingplanet.com/netsp/article.php/3617346/Networking-101--Understanding-iBGP.htm

 

The network where I work is kinda of different than usual, its all BGP. Not your typical setup. We do have 3 datacenters (2 really, 1 is tiny) with DR replication/failover between them etc.

What's your professions, I'm assuming its IT related?

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Yeah I was reading up on this, BGP is typically used in large corporations to link multiple internal networks as well therefore making it a somewhat hybrid protocol since it can technically be used as an IGP as well as an EGP.

 

 

Have a read of this, http://www.enterprisenetworkingplanet.com/netsp/article.php/3617346/Networking-101--Understanding-iBGP.htm

 

The network where I work is kinda of different than usual, its all BGP. Not your typical setup. We do have 3 datacenters (2 really, 1 is tiny) with DR replication/failover between them etc.

I'd stay away from BGP if you are just wanting to learn the core protocols. BGP is a whole other beast. Focus on RIP, OSPF, and EIGRP. You can take a look at BGP but it's kind of like a red pill blue pill scenario here.  Choose to start learning BGP and you'll see how deep the rabbit hole really goes. Also just a heads up that link only concerns iBGP (internal BGP). It is an important part of the core protocol to know if you chose to go that route but it is not even half of the basics.

 

If you want to learn networking/IT and have some fun with it (you said your N+ book was pretty dry) try CBT Nuggets. You can get a 7day free trial per email. Give it a try, it is the best online IT training I've ever used.

 

https://www.cbtnuggets.com

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What's your professions, I'm assuming its IT related?

 

Systems Engineer at a University. Previous job was in an IT Services/Consulting company that worked in the education sector. Don't do much networking in my current job but did a fair amount of networking in my old position, nothing on the scale of my current work's network. Networking has never been my primary role or focus, just something I have studied and picked up over time.

 

My hands on networking experience is on networks with around 2000 users, 500-1000 desktop computers and 50+ managed Aruba wireless points serving few hundred wireless clients. Jack of all trades, master of nothing :). Networking was actually a smaller part of the work I did, mostly in server deployment and desktop management areas.

 

University I work at now has around 33000 student users and 3000 staff users. 

 

I also worked with VMware, Hyper-V, Cisco, HP, Allied Telesis, Aruba, Ruckus, CommVault, SCCM, SCOM... list is actually kinda large now that I think about it so I'll stop listing them :P

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I'd stay away from BGP if you are just wanting to learn the core protocols.

 

Yep agree with that statement. I'd listen to @Wombo's advice more than mine, I'm willing to bet hes got more experience in networking than I do :P.

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Systems Engineer at a University. Previous job was in an IT Services/Consulting company that worked in the education sector. Don't do much networking in my current job but did a fair amount of networking in my old position, nothing on the scale of my current work's network. Networking has never been my primary role or focus, just something I have studied and picked up over time.

 

My hands on networking experience is on networks with around 2000 users, 500-1000 desktop computers and 50+ managed Aruba wireless points serving few hundred wireless clients. Jack of all trades, master of nothing :). Networking was actually a smaller part of the work I did, mostly in server deployment and desktop management areas.

 

University I work at now has around 33000 student users and 3000 staff users. 

 

I also worked with VMware, Hyper-V, Cisco, HP, Allied Telesis, Aruba, Ruckus, CommVault, SCCM, SCOM... list is actually kinda large now that I think about it so I'll stop listing them :P

 

 

I'd stay away from BGP if you are just wanting to learn the core protocols. BGP is a whole other beast. Focus on RIP, OSPF, and EIGRP. You can take a look at BGP but it's kind of like a red pill blue pill scenario here.  Choose to start learning BGP and you'll see how deep the rabbit hole really goes. Also just a heads up that link only concerns iBGP (internal BGP). It is an important part of the core protocol to know if you chose to go that route but it is not even half of the basics.

 

If you want to learn networking/IT and have some fun with it (you said your N+ book was pretty dry) try CBT Nuggets. You can get a 7day free trial per email. Give it a try, it is the best online IT training I've ever used.

 

https://www.cbtnuggets.com

Wombo the networking god has spoken! Thank you both very much, it helps more than you think!

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Wombo the networking god has spoken! Thank you both very much, it helps more than you think!

Hahaha. I now have a candidate for a title once I reach 500 posts.

 

And thanks. It's always rewarding to share knowledge.

 

Edit: Thought I'd share one of my favorite links from back when I was learning the basics of routing protocols. This list is very useful, within a Cisco context anyway.

 

http://cisconet.com/routing/routing-general/116-list-of-routing-protocol-administrative-distance-value.html

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I agree with Wombo, avoid BGP for the time being. As an ISP we use BGP to our upstream peers, but use ISIS in our transport network, and OSPF in some areas to support some older cisco gear that does not support ISIS. ISIS is a newer protocol that scales better than OSPF. As a service provider this was a big advantage. Routing protocols are an important piece of large networks and you can use multiple protocols. Our ISIS routes are able to share over to OSPF and vice versa.

 

Take the time to learn routing and it's protocols. We have a customer, a local government IT group, that has a massive layer 2 network around the entire city. They have constant issues all because they have no one that understands routing. When I started at this ISP 10 years ago one of the previous engineers had used static routes all over the network and it took years to clean that up. 

 

Good luck in your endeavors. 

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I agree with Wombo, avoid BGP for the time being. As an ISP we use BGP to our upstream peers, but use ISIS in our transport network, and OSPF in some areas to support some older cisco gear that does not support ISIS. ISIS is a newer protocol that scales better than OSPF. As a service provider this was a big advantage. Routing protocols are an important piece of large networks and you can use multiple protocols. Our ISIS routes are able to share over to OSPF and vice versa.

 

Take the time to learn routing and it's protocols. We have a customer, a local government IT group, that has a massive layer 2 network around the entire city. They have constant issues all because they have no one that understands routing. When I started at this ISP 10 years ago one of the previous engineers had used static routes all over the network and it took years to clean that up. 

 

Good luck in your endeavors. 

I've always heard i-IS-IS was popular however I thought it was more of an older choice to align with certain regulations, in the US in particular, that carriers were required to run IS-IS in some capacity as their IGP. I've always had a bit of aversion to IS-IS just due to its integrated nature. From your experiences what are your reasons for preferring i-IS-IS over OSPF or EIGRP? I've heard the flexible backbone created via the level 2 routers/database makes for easier expansion, but I'd like to hear what you feel the benefits are within your environment.

 

Also you had stated that IS-IS was a newer protocol. Support for it on certain devices may have only became available recently (oddity) however i-IS-IS was released with RFC 1195 in December of 1990. While the original OSPF v1 was released in October of 1989 it was redacted and considered obsolete with the release of OSPF v2 within RFC 1247 in July of 1991. This was later eclipsed by several improvements and ratification the most recent of which is RFC 7474 with was released in April of 2015. The last RFC for integrated IS-IS was RFC 6232 in July of 2011.

 

https://tools.ietf.org/html/rfc7474

https://tools.ietf.org/html/rfc6232

 

I just want to make sure I don't come across as rude or anything but I am wondering what you mean by IS-IS being a newer protocol.

 

I don't get to talk with many network engineers so I have to jump at this chance.

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I agree with Wombo, avoid BGP for the time being. As an ISP we use BGP to our upstream peers, but use ISIS in our transport network, and OSPF in some areas to support some older cisco gear that does not support ISIS. ISIS is a newer protocol that scales better than OSPF. As a service provider this was a big advantage. Routing protocols are an important piece of large networks and you can use multiple protocols. Our ISIS routes are able to share over to OSPF and vice versa.

 

Take the time to learn routing and it's protocols. We have a customer, a local government IT group, that has a massive layer 2 network around the entire city. They have constant issues all because they have no one that understands routing. When I started at this ISP 10 years ago one of the previous engineers had used static routes all over the network and it took years to clean that up. 

 

Good luck in your endeavors. 

Thanks a lot for the advice, i'll definitely focus on those protocols for sure, the only reason I'm interested in BGP at the moment is because its an exam objective. Thanks a lot!

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Thanks a lot for the advice, i'll definitely focus on those protocols for sure, the only reason I'm interested in BGP at the moment is because its an exam objective. Thanks a lot!

You said you're doing the N+ correct? When I took mine last year I don't remember getting a single question on any routing protocols. The N+ is very focused on small business and consumer products and services so I can't really see BGP being a big topic.

 

I'd probably say the important things of note for BGP (conceptually) are:

 

It is THE exterior gateway protocol of the internet, there really aren't any others in use, at least not in volume.

The routing table is MASSIVE, over 500,000 routes currently (IPv4).

It is only needed when you require redundant downstream connectivity from multiple providers. Ex. you have web servers hosted locally that need to be available publicly even in the event one of your providers goes down.

Modern implementations of Multi-protocol BGP (mBGP) allow for the transport of almost anything, not just IPv4 or IPv6.

BGP requires a lot of manual tweaking and is not an easy protocol to use.

Unless you are an ISP or a truly massive corporation you won't need BGP.

 

Edit: Reading the N+ exam objectives it seems all they really want is for you to know what the differences are between link-state and distance-vector routing protocols and then to palce them under the umbrellas of IGP (interior gateway protocol) or EGP (exterior gateway protocol).

 

Distance vector - I only know what my neighbors have told me. Sometimes called "routing by rumor". I use this information to determine how to route traffic. Less demanding on CPU and memory.

Link State - I know all the information about every link (within an area or database) and I make my own choice on what path is the best. Everyone within the same area/database will have the exact same "map" or topology of how the network looks. More demanding on CPU and memory.

Hybrid - Takes some of both. Varies by protocol. Ex. EIGRP combines some of the less demanding aspects of distance vector and combines it with the faster convergence and ability to have "backup" routes that link state can provide.

 

Also, you may like this playlist. The entire N+ exam objectives covered, free on YouTube (Updated for the new objectives, 2015).

https://www.youtube.com/playlist?list=PLG49S3nxzAnnXcPUJbwikr2xAcmKljbnQ

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You said you're doing the N+ correct? When I took mine last year I don't remember getting a single question on any routing protocols. The N+ is very focused on small business and consumer products and services so I can't really see BGP being a big topic.

 

I'd probably say the important things of note for BGP (conceptually) are:

 

It is THE exterior gateway protocol of the internet, there really aren't any others in use, at least not in volume.

The routing table is MASSIVE, over 500,000 routes currently (IPv4).

It is only needed when you require redundant downstream connectivity from multiple providers. Ex. you have web servers hosted locally that need to be available publicly even in the event one of your providers goes down.

Modern implementations of Multi-protocol BGP (mBGP) allow for the transport of almost anything, not just IPv4 or IPv6.

BGP requires a lot of manual tweaking and is not an easy protocol to use.

Unless you are an ISP or a truly massive corporation you won't need BGP.

 

Edit: Reading the N+ exam objectives it seems all they really want is for you to know what the differences are between link-state and distance-vector routing protocols and then to palce them under the umbrellas of IGP (interior gateway protocol) or EGP (exterior gateway protocol).

 

Distance vector - I only know what my neighbors have told me. Sometimes called "routing by rumor". I use this information to determine how to route traffic. Less demanding on CPU and memory.

Link State - I know all the information about every link (within an area or database) and I make my own choice on what path is the best. Everyone within the same area/database will have the exact same "map" or topology of how the network looks. More demanding on CPU and memory.

Hybrid - Takes some of both. Varies by protocol. Ex. EIGRP combines some of the less demanding aspects of distance vector and combines it with the faster convergence and ability to have "backup" routes that link state can provide.

 

Also, you may like this playlist. The entire N+ exam objectives covered, free on YouTube (Updated for the new objectives, 2015).

https://www.youtube.com/playlist?list=PLG49S3nxzAnnXcPUJbwikr2xAcmKljbnQ

Thanks a lot man! I really should't spend so much time on the protocols because I have the basics down so I should move along and get the rest of the basics down. I can always expand my knowledge after the test, but judging from your advice I think I'm pretty solid. Thanks Wombo!

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Thanks a lot man! I really should't spend so much time on the protocols because I have the basics down so I should move along and get the rest of the basics down. I can always expand my knowledge after the test, but judging from your advice I think I'm pretty solid. Thanks Wombo!

Yup the N+ is all about a basic level of knowledge and an understanding of what things are at an abstract level, not so much how they really work. You're definitely on the right track. Goodluck with your studies.

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I've always heard i-IS-IS was popular however I thought it was more of an older choice to align with certain regulations, in the US in particular, that carriers were required to run IS-IS in some capacity as their IGP. I've always had a bit of aversion to IS-IS just due to its integrated nature. From your experiences what are your reasons for preferring i-IS-IS over OSPF or EIGRP? I've heard the flexible backbone created via the level 2 routers/database makes for easier expansion, but I'd like to hear what you feel the benefits are within your environment.

 

Also you had stated that IS-IS was a newer protocol. Support for it on certain devices may have only became available recently (oddity) however i-IS-IS was released with RFC 1195 in December of 1990. While the original OSPF v1 was released in October of 1989 it was redacted and considered obsolete with the release of OSPF v2 within RFC 1247 in July of 1991. This was later eclipsed by several improvements and ratification the most recent of which is RFC 7474 with was released in April of 2015. The last RFC for integrated IS-IS was RFC 6232 in July of 2011.

 

https://tools.ietf.org/html/rfc7474

https://tools.ietf.org/html/rfc6232

 

I just want to make sure I don't come across as rude or anything but I am wondering what you mean by IS-IS being a newer protocol.

 

I don't get to talk with many network engineers so I have to jump at this chance.

Thanks Wombo, Sorry I did not respond right away I have been out of town. 

 

So you are correct ISIS as an RFC has been around for a while, I should have clarified that it was new to me. We did not however implement ISIS as any sort of regulation. The main reason we implemented ISIS was due to it's ability to handle more routers per area with less overhead, as well as to get to a sub 50ms convergence on link failure. We have multiple ethernet rings and we initially used ERP and OSPF but had convergence in the neighborhood of 300-800 ms. As a result we worked with our vendor and rebuilt our network using ISIS. So far we have what we were looking for. Typically large networks work better with ISIS  and hence the reason it is used by many High tier ISP's here in the US. 

 

I don't think you were being rude and appreciate the inquiry. In fact when our vendor recommended the change I was not too happy about it considering I knew OSPF, however in the 6 months since we've been running it and our issues have dropped substantially I actually am very pleased with ISIS. Could we have made OSPF work? Most likely but when a vendor recommends something you best implement it. 

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Thanks Wombo, Sorry I did not respond right away I have been out of town. 

 

So you are correct ISIS as an RFC has been around for a while, I should have clarified that it was new to me. We did not however implement ISIS as any sort of regulation. The main reason we implemented ISIS was due to it's ability to handle more routers per area with less overhead, as well as to get to a sub 50ms convergence on link failure. We have multiple ethernet rings and we initially used ERP and OSPF but had convergence in the neighborhood of 300-800 ms. As a result we worked with our vendor and rebuilt our network using ISIS. So far we have what we were looking for. Typically large networks work better with ISIS  and hence the reason it is used by many High tier ISP's here in the US. 

 

I don't think you were being rude and appreciate the inquiry. In fact when our vendor recommended the change I was not too happy about it considering I knew OSPF, however in the 6 months since we've been running it and our issues have dropped substantially I actually am very pleased with ISIS. Could we have made OSPF work? Most likely but when a vendor recommends something you best implement it. 

I feel IS-IS is new to most people. Every time it's brought up there's bound be a few people that have never even heard of it before. A 50ms convergence time is pretty damn great and is very important to have it as low as possible when dealing with core equipment. Seems like the switch was great for you guys.

 

Thanks for the response, it's always great to hear what engineers are doing in other networks around the world.

 

I just hope I don't get forced to learn IS-IS in depth. I understand the core of it and can configure it to run but I just don't like those pesky OSI addresses.

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  • 2 weeks later...

Oh, do I long for the days of Token Ring and Banyan Vines  :rolleyes:  No... not really...

Forum Links - Community Standards, Privacy Policy, FAQ, Features Suggestions, Bug and Issues.

Folding/Boinc Info - Check out the Folding and Boinc Section, read the Folding Install thread and the Folding FAQ. Info on Boinc is here. Don't forget to join team 223518. Check out other users Folding Rigs for ideas. Don't forget to follow the @LTTCompute for updates and other random posts about the various teams.

Follow me on Twitter for updates @Whaler_99

 

 

 

 

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