Routing between eigrp and ospf same subnet

[NetworkGuy!]

Hi 

Scenario here is 

                                                              Cisco Firewall 10.10.10.4 (vlan 10)

                                                                      |

                                                                      | 

                                                                      EIGRP

                                                                      |

                                                                       |

Cisco Switch--------EIGRP---------Cisco Switch------ospf---------Juniper Firewall

10.10.10.1                                            10.10.10.2                                         10.10.10.3

Vlan 10                                                   Vlan 10                                                Vlan 10

Can the juniper firewall be on same vlan 10 as others but running ospf between core switch and juniper? other cisco devices are running eigrp

[Seb Rupik]

Hi there,

Yes. Both routing protocols use different multicast groups for communications so there is no risk of interference.

The core switch will need to be configured with both a EIGRP and OSFP routing process and you will need to configure the redistribution of routes between them.

cheers,

Seb.

[paul driver]

Hello

The assumption here is the cisco core is doing the routing- correct?
The routing protocols wont have any affect ,All connectivity will be via L2, assuming again the same ip addressing is being used is on the fw, cisco and juniper? , Even if that isnt the case the core switch will route via each SVI

The only time I can see that routing protocols will be applicable is if the cisco and juniper switches are in different subnets and no SVI;s are in use, meaning pure L3

[Deepak Kumar]

Hi,

As everyone is mentioned that there will no issue because both routing protocols are working on different multicast group. 

But keep in mind that if you want to share routes between EIGRP and OSPF then must configure redistribution between each other. 

Question: Why would you required OSPF and EIGRP because I can see that all Switches and Firewall on the Same VLAN?

Regards,

Deepak Kumar

[paul driver]

Hello

---

@Deepak Kumar wrote:

As everyone is mentioned that there will no issue because both routing protocols are working on different multicast group. 

---

I would tend to steer towards the reason why these two routing protocols wont understand each other is down to their protocol design and different metric calculation, Eigrp is based on a metric cost relating to the whole path towards a route and ospf based is on metric cost per link so unless redistribution is performed they would have no way of understating each other.

Its true although eigrp and ospf don't share the same MC addressing but then neither does any other feature that may be running with a MC address such as HRSP, PIM etc.

[Richard Burts]

The original post asks a fairly simple question about whether the core switch can run OSPF with a Juniper firewall while it is running EIGRP with Cisco devices and all in the same subnet. The responses are unanimous that yes this can be done. The drawing suggests a perhaps somewhat complicated environment with a Cisco firewall and a Juniper firewall. And it makes me wonder if under the surface of the simple original question is a more complicated question about how this will work and will it achieve some desired objective? Since we do not know what the desired objective is we can not address whether this will achieve it. But we can make some comments about how this will work.

As shown the core switch will maintain topology tables for both EIGRP and for OSPF and the routing table will have routes learned from Cisco devices and routes learned from Juniper. So the core switch will have routing information about both domains and can route between the domains. The Cisco devices (the firewall and other Cisco devices) will have routing information about routes originated on Cisco devices but will have no information about routes originated from Juniper. The Juniper will have routing information about its own routes but will have no information about routes originated from Cisco devices.

HTH

Rick

[Deepak Kumar]

Hi @Richard Burts 

Thanks for your reply. I like your words and you are good in English. Are you an author of a book? 

As I got your reply you said the same thing. Yes, It is possible and by default EIGRP will not learn OSPF routes and vice-versa.  

Regards,

Deepak Kumar

[Richard Burts]

@Deepak Kumar Thank you for the kind words. I have been a technical editor for several books. But I have not authored a book myself.

Yes the two routing protocols operate independently. They both share the same vlan and same subnet. So the Juniper will see the EIGRP packets and will ignore them. The Cisco (other than the core switch) will see the OSPF packets and will ignore them. So neither protocol has any effect on the other protocol.

HTH

Rick

[paul driver]

Hello rick

@NetworkGuy!   Wrote:

isco Switch--------EIGRP---------Cisco Switch------ospf---------Juniper Firewall

10.10.10.1                                            10.10.10.2                                         10.10.10.3

Vlan 10                                                   Vlan 10                                                Vlan 10

Can the juniper firewall be on same vlan 10 as others but running ospf between core switch and juniper? other cisco devices are running eigrp

---

The Op asked the question regard all 3 devices being in the same vlan and what looks like the same subet also so that being said I meraly pointed out that no igp would be applicable even if they were enabled they wouldn’t be used due to the fact all communication would be L2 between Cisco Asa and juniper and they would all be able to communicate now if we assume there are other networks behind the jumper Cisco etc then of course igp redistribution would be applicable 

lastly regards the multicast addressing again I was pointing out that just because  eigrp and ospf have different addressing dosent mean thats the reason two igps won’t  be able to communicate 

[Richard Burts]

Paul

You appear to interpret the question in the original post differently from what I do. You seem to think that the question is whether a routing protocol is required for the devices to communicate. And I most certainly agree with you about the fact that no routing protocol is required for them to communicate since they are in the same vlan and in same subnet. I interpret the question to be asking if EIGRP and OSPF can both be running in the same vlan/same subnet at the same time. Certainly both protocols can run here. EIGRP neighbor relationship will be formed between the Cisco devices. And OSPF neighbor relationship will be formed between Juniper and core switch. How effective they are and what will be advertised depends on what else they are connected to and what other routes they know. But both protocols can run on same vlan/same subnet at the same time.

HTH

Rick

[sagarvogatti]

@Richard Burts 

Lastly what you mention absolutely correct. Even they are in same VLAN but IGP are different. Everything will come to core switch so EIGRP and OSPF will not conflict. @NetworkGuy!  Yes you can do what you asked for.

Thanks!

Regards,

Sagar Bairagi

CCIE#57252

[Deepak Kumar]

Hi,
Thanks for extending my answer in more depth.

Regards,
Deepak Kumar