Kiến thức về các giao thức định tuyến và việc cấu hình, troubleshooting chắc nhiều anh
em ngon rồi và cũng có tài liệu hướng dẫn cụ thể và cơ bản rồi. Tuy nhiên việc vận dụng
vào thực tế vẫn là một vấn đề cần nhiều kinh nghiệm.
Việc lựa chọn EIGRP hay OFPF trong các mạng thực tế đang là một vấn đề tương đối
phức tạp, xin được mọi người đóng góp ý kiến trao đổi.
Dưới đây là một số quan điểm khác nhau của Tây
EIGRP is proprietary to Cisco. OSPF is open standard.
Each has advantages and disadvantages and depends on the environment.
EIGRP is a lot easer to implement than OSPF. If you have an all, mostly Cisco
environment it is probably the way to go. Now if you have a mixed environment of
several different brands of routers OSPF, or BGP make better sense since they are open
protocols. Also you can cross over on edge routers to other protocols, that is the way I
have it set up on my network, BGP to the net on the my edge router and EIGRP for my
own network. One thing, if you do go with EIGRP make sure you disable auto
summarization of networks on stub routers, it’s of no use for them and a lot of times they
end up advertising an entire network in their routes even if it has been submitted.
I dissagree with DrIP's comment saying that EIGRP is easier than OSPF. Both are very
simple to confiure for average sized simple topology networks, and both can be very
complicated on intricate and large topologies.
OSPF uses less bandwidth than EIGRP. EIGRP is NOT link state, not even "with linkstate features" like Cisco likes to comment. OSPF is standards based, EIGRP is
proprietary.
BGP is a different class of protocol altogether, and shouldn't even be considered a viable
solution for most internal networks.
You choose routing protocols depending on the way that your network topology is. If you
have a large topology with many branch offices that have smaller offices of their own,
then you would probably use OSPF. If you have a topology where you have one
corporate office with maybe 25 smaller offices lets say, then you would probably
implement EIGRP
I would say that EIGRP and OSPF can be used in equally large networks. Both have
there ups and downs. Usually the primary deciding factor is whether or not you have all
Cisco equipment and if things are going to stay that way for a while. Which produces
more traffic is arguable and depends greatly on topology and configuration.
While it is true that EIGRP is not a link state protocol, it employs many of the features
people associate with link state protocols, which is why it is often referred to as a hybrid
protocol. It is a distance-vector protocol with the features of a link state protocol. It just
doesn't use link state as its means to determine a routing table.
EIGRP can handle several LAN protocols (IP, IPX, Appletalk... maybe others), OSPF is
IP only. EIGRP is expecially well suited for IPX environments
One thing I like about OSPF, even in a 100% Cisco network, is the fact the network is set
up in areas. The effects of 'troubles' in one area are contained, thus does not cause
unneccessary router computation in the other stables areas. EIGRP does not offer this.
Thus trouble in 'Atlantic Canada', would cause all the routers across the country to
performs routing table computation, but OSPF would keep this in Atlantic Canada.
It takes a lot of goods planning upfront with OSPF, it does have some strick
requirements. A well designed OSPF network is "sweet", and a poorly designed OSPF
network can be a "living nightmare".
**
go in straight way for eigrp if having 20 cicco routers.
ospf is slightly complex and well suited for large networks.
ease of operatibility is there in eigrp.
if going in for eigrp dont forget to disable the auto summarisation option.
**
OSPF all the way, unless technical requirements dictate EIGRP for optimized
convergence, or other reasons.
OSPF is so much easier to integrate other networks and vendors equiment if requirements
change down the road. Otherwise it's rework. OSPF is fairly complex under the covers,
but that's just for a little entertainment! 20 routers is a very small number and could easily
run all 20 in one area if you needed to.
**
EIGRP? Hehe. In most case I like OSPF, I've designed hundreds of Cisco routers running
OSPF, while EIGRP is only for some special situations which might have to redistribute
some routes each other. OSPF is much easier and clear.
**
Yes, Eigrp support VLSM and classless routing features, it doesn't mean it is hierarchal
routing protocol. Like I said, through the carefully planning and design, the EIGRP can
behave like a hierachal routing protocol, like OSPF.
Discussing which routing protocol is more prior to another one is meaningless, it depends
on the situations. 20 or more routers can be run very well under RIP too, the key points
are how many routing entries in the routing table and how stable and how fast the route
could be! Another thing is how to balance the cost due to the routing protocols' cost.
If a customer wants a quick convergencied network, you may consider using EIGRP; if
customer wants to deal with different vendors, OSPF might be your choice; if MPLS is
needed in customer's network, you may think OSPF or IS-IS; if customer just want a
simple network and be easy to dig in, RIP could be the best choice.
**
It sounds good if all cisco routers are used in a network, what if your customer wants to
implement BGP/MPLS VPN on someday?
EIGRP is not recommanded as intra autonomous backbone routing protocol. So, this is an
example of technical constraint of the routing protocol.
Under the above situation, either ospf or isis should be considered.