EIGRP Router

AXISHK
AXISHK used Ask the Experts™
on
What does  the following command mean
#1  redistribute connected
#2  eigrp stub connected summary
#3  In EIGRP, only "network 10.50.10.5 0.0.0.0" is included but I find that VLAN 3 can route to VLAN 6. How does it work ?


interface Vlan1
 ip address 192.168.100.252 255.255.255.0

!
interface Vlan3
 ip address 10.50.10.5 255.255.254.0
 ip helper-address 192.168.100.240
!
interface Vlan4
 ip address 10.50.21.1 255.255.255.0
!
interface Vlan5
 ip address 10.50.20.1 255.255.255.0
!
interface Vlan6
 ip address 10.50.30.1 255.255.255.0
 ip helper-address 10.50.10.21
!
!
router eigrp 2
 redistribute connected
 eigrp stub connected summary
 network 10.50.10.5 0.0.0.0
!
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Top Expert 2015
Commented:
#1  redistribute connected   -- redistributing the connected networks(with subnet masks) assigned to interface into the EIGRP routing table

Usually the router will have connected, static and dynamic routes in the routing table.  if you want the connected networks/static needs to participate in the dynamic routing table, we need to redistribute it.

#2  eigrp stub connected summary  -->
"eigrp stub connected" stops advertising summary routes, and "eigrp stub summary" will stop
advertise connected.

#3  In EIGRP, only "network 10.50.10.5 0.0.0.0" is included but I find that VLAN 3 can route to VLAN 6. How does it work ?    -- VLAN3 and VLAN6 are in the same router; Hence both VLAN networks will be in connected routing table and each other can ping without EIGRP
Distinguished Expert 2018

Commented:
#2  eigrp stub connected summary  -->
"eigrp stub connected" stops advertising summary routes, and "eigrp stub summary" will stop advertise connected.
Just the opposite. Router is marked as stub router (one of the ways to prevent stuck in active (SIA)), and router will advertise just connected and summary routes.

router eigrp 2
network 10.50.10.5 0.0.0.0
will perform two things - it will advertise 10.0.0.0/8 network in eigrp AS 2 (since there is no command no auto-summary - auto summary is default option), and it will advertise it just on interface with IP address 10.50.10.5 (subnet mask 0.0.0.0 means - exactly this address)

VLAN3 and VLAN6 are in the same router; Hence both VLAN networks will be in connected routing table and each other can ping without EIGRP
This is true if ip routing is enabled (ip routing is default for Cisco routers for IPv4)

Author

Commented:
Thanks

#1 What's the point of using EIGRP if these VLANs can be routed within themselves ?

#2 Is the switch is connected to another switch through trunk port, do I need to add EIGRP routing ?
 
#3 redistribute connected... does it also include static and virtual interface, or just the physical connected interface

#4 Router is marked as stub router and router will advertise just connected and summary routes. Does you mean the my multi-layer switches ?

Tks
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Top Expert 2015

Commented:
Connected routes can communicate within the device only. If you have two sites and if you want both sites to communicate each other , then u need EIGRP(or other dynamic routing protocol)

#2 --- no need to enable EIGRP on the access switches

#3 --- redistribute connected will not advertise static routes. For redistributing the static routes you need to use "redistribute static " command

#4 --- yes

Author

Commented:
#3 redistribute only advertise physical interface, how about virtual interface ? Tks
Distinguished Expert 2018
Commented:
With EIGRP network command you can always advertise any attached interface (AD 90), but redistribute connected will also advertise virtual interfaces (loopback, tunnel, subinterfaces - since those are connected interfaces) as external networks with AD 170.

And actually command # redistribute connected as it is configured in your post will not advertise any connected interface (it will, but it will advertise connected interfaces with infinite metric, so those routes will not be accepted by any neighbor router).
For redistribution into EIGRP you must set seed metric, if seed metric is not set redistributed routes are advertised with infinite metric.

Author

Commented:
tks

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