eigrp-or-ospf-which-should-i-use
.pdf
EIGRP Hub and Spoke
Marking these remotes as stubs also reduces the topological complexity
(meshiness) of the network
Without stub configuration on spokes, B believes it has five paths to 10.1.1.0/24,
so it has to maintain
five topology table entries
10.1.1.0/24 |
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© 2008 Cisco Systems, Inc. All rights reserved. |
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EIGRP Hub and Spoke
Routers which are configured as EIGRP stubs will only advertise locally connected or redistributed destinations
These remotes will not pass
A’s advertisement of
10.1.1.0/24 to B
B will only have one path to 10.1.1.0/24
10.1.1.0/24 |
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© 2008 Cisco Systems, Inc. All rights reserved. |
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Full Mesh
Full mesh topologies are complex:
2 routers = 1 link
3 routers = 3 links
4 routers = 6 links
5 routers = 10 links
6 routers = 15 links
…
Adjacencies = links(links-1)/2
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© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
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OSPF Full Mesh
Flooding routing information through a full mesh topology is also complicated
Each router will, with optimal timing, receive at least one copy of every new piece of information from each neighbor on the full mesh
OSPF uses notion of Designated Router (DR) to improve scalability in mesh networks
New Information
© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
34 |
EIGRP Full Mesh
Routes must be advertised between every pair of peers in the mesh so each router has the correct next hop and routing information
Number the links so they can be summarized to a single advertisement at the edge
Good for smaller mesh networks, summarization more important for larger mesh networks
Summarize
Summarize |
Summarize |
Summarize |
Summarize |
Summarize
© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
35 |
OSPF Support for Hierarchy
OSPF requires a hierarchical design
Summarization and filtering occur at flooding domain borders
Summarization and filtering can also be configured at routers redistributing routes into OSPF
In a two layer hierarchy, the flooding domain border naturally lies on the aggregation/core boundary
Summarization
area 0
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© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
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EIGRP Support for Hierarchy
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EIGRP does not require a |
Core |
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heirarchical design |
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Auto-summarization enabled |
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by default at classful network |
Distribution |
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boundaries |
Summarization |
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EIGRP enables you to |
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summarize at any desired |
Access |
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boundary |
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Proper network design is still |
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needed! |
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© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
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Topology Summary
Rules of Thumb
EIGRP performs better in large scale hub and spoke environments
OSPF perform better in large full mesh environments, if tuned correctly
EIGRP tends to perform better in more strongly hierarchical network models, OSPF in flatter networks
© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
38 |
Other Considerations - 1
EIGRP forms adjacencies and exchanges routing updates with neighbors
OSPF forms adjacencies with DR/BDR
OSPF can be more efficient than EIGRP for large meshed networks
EIGRP uses metric based on bandwidth and delay
OSPF uses interface cost (inversely proportional to bandwidth)
EIGRP may provide more flexibility in selecting best path
EIGRP by default limits usage to at most 50% of link bandwidth in worst case
OSPF uses 100% of link bandwidth when required
EIGRP may be better suited for lower bandwidth WAN applications
EIGRP provides feature velocity, but is Cisco-proprietary
OSPF is an Internet RFC standard
© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
39 |
Other Considerations - 2
EIGRP sends hop-by-hop queries only when Feasible Successor cannot be found
OSPF regularly syncs LSA database and floods network with topology change
EIGRP can be more efficient by minimizing routing information exchanged
EIGRP is a conceptually simpler routing protocol
OSPF’s rules for different types of areas and LSAs can be conceptually more difficult to understand
Some customers believe EIGRP is easier to implement, but both are feature-rich and scalable
EIGRP supports automatic summarization
OSPF’s requires manual summarization
Care is needed in either case to ensure proper summarization!
EIGRP supports both equal and unequal cost load sharing
OSPF only supports equal cost load sharing
© 2008 Cisco Systems, Inc. All rights reserved. |
Cisco Public |
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