Cisco 7500 Question

[mounir.mohamed]

Dear All,

My questions regarding Cisco 7500 series router, due to design and redundancy requirements we need to cross 4 7500 (2-7507 and 2-7513) routers with each others via Giga-Ethernet interfaces, so I have to install 2 Giga-Ethernet interfaces on each one of them, Also note that each router already has 3 VIP's and each VIP has 2 PA-A3-OC3MM interfaces up and operational.

As per Cisco specification for this series (7507-7513), the maximum number of Giga-Ethernet interfaces that can be installed is 2.

Now, will the router performance be degraded after install 2 Giga-Ethernet on each router, Even if each Giga Interface is installed on independent VIP?

(NOTE - The maximum traffic rate on each Giga-Ethernet interface will be 500M no more, so we are still under the maximum bandwidth supported by backplane, which is 2G)

Best Regards,

Mounir Mohamed

[marikakis]

Hello,

This is an ambitious plan with 7500's. These routers are simply unpredictable. (I hope they will just go away :-) A slight increase in the traffic of a single interface can make a difference in router performance. It basically depends on the network architecture and traffic patterns. For example, if all your ATM interfaces are feeding a single GigabitEthernet (hub-and-spoke style), then your router is more susceptible to slight traffic changes than it would be if 2 ATM's on the same VIP would be exchanging traffic with each other.

Since you want this for redundancy, you could risk it, but those GigabitEthernet interfaces and the maintenance procedure are not free. And let's not forget, that every time you touch a 7500, you should be ready to pay the consequences. So, if you are going to do it anyway, make sure the redundancy does have chances of working at least with a failure in a single router.

2G is the theory (some overhead cycles in a bus are always there, some cycles are wasted) and if I remember correctly (have to check my books), these models have 2 internal buses, so 2G is the sum of the theoretical bandwidth of those 2 buses. Perhaps you could try (besides throwing away the 7500's, ok I am a bit obsessed), balancing your cards over the 2 buses, to avoid having your router lean towards the one side. You should also take into consideration the case of failure in another router. Problem is I do not remember which slot attaches to which bus (could guess, but I won't), and cannot find this information in cisco.com, but I am quite sure I have it somewhere at home. Unless somebody else has this information at hand, I will check it out tonight and I will inform you.

Kind Regards,

M.

[mounir.mohamed]

Dear Mark,

First of all thanks for your fast response.

Actually in the current situation the ATM interface used to aggregate multiple remote-side PE routers and one of the Gigabit-interfaces used for upstream traffic between them, the second Gigabit-interface used for redundancy only so now the total traffic over all ATM PA's on each router will be maximum 450M and the total traffic over Gigabit interfaces will be 500M.

So are we saved to use all this combination of interfaces?

Best Regards,

Mounir Mohamed

[marikakis]

Hello,

I think you will be ok, basically because the 2nd GigabitEthernet will not be active most of the time. I do stress the "think" part, since I cannot be absolutely sure.

Here is what I would do. I would put the VIP's with the ATM OC3 PA's on the one bus of the 7500 and the GigabitEthernets on the other. The logic is that you balance your traffic across the 2 internal buses, allowing for some future growth and expecting that the one of the two GigabitEthernets will not be active most of the time (only in failure cases). If you accidentally have all your cards on a single internal bus, then that bus can be soon overwhelmed, since it can go up to 1G, while the other remains inactive.

As I said in my previous post, I need to lookup some information about slot assignment to internal buses that I do not have access to right now and I will inform you. Trying to balance the PA's across the buses maybe a cumbersome task, but I would try to do it as much as possible, since I prefer not leaving too many things to chance. If one of your routers is suddenly hit by the backbone traffic of another of your routers, this is a 500Mbps risk. Of course this is a failure situation, but there might be cases when one prefers having 1 router down than 2 or more (sometimes failures come in domino style).

Kind Regards,

M.

[mounir.mohamed]

Yes i'm usually distribute my VIP's and active/standby PA's on differnet buses not only on 7500 but also on 7200 or any Shared bus gears in order to save large number of bandwidth points issues and more...etc

Anyway please feed me back when u reach your notes.

Thanks

Best Regards,

Mounir Mohamed

[marikakis]

Hello,

I finally found the information on cisco.com as well, which is better than relying on my old notes from year 2002 just because I say so. I had only written down the information about the 7507 model anyway. :-)

Cisco 7507 Dual CyBus Backplane :

http://www.cisco.com/en/US/products/hw/routers/ps359/products_installation_and_configuration_guide_chapter09186a00801c63a5.html#wp1038394

Cisco 7513 Dual CyBus Backplane :

http://www.cisco.com/en/US/products/hw/routers/ps359/products_installation_and_configuration_guide_chapter09186a00801c63a5.html#wp1038723

Kind Regards,

M.

[mounir.mohamed]

Both URL's redirect to the same page :)

Thanks, i will kill it

[marikakis]

Yes, that's right, but they are supposed to be different pointers inside the same page, so that you can directly see the information about the 2 different 7500 models you have without you searching down the document. I was trying to be extra helpful and now you are making fun of me :-)))

Good Luck! Anyone dealing with 7500's needs it!

[mounir.mohamed]

Dear Mark,

SURE NO, I never Mean that, really i'm appreciate your helpful information, Do not take it like that man, the man should never assume :)) and i beleive the points reflect my appreciation, finally thanks man for such great URL.

Thanks

Best Regards,

Mounir Mohamed

[marikakis · Accepted solution]

Yes, I know you meant well, I was just making a joke. I do try not to assume, although it is sometimes hard for me, because I am a woman. :-)))

[mounir.mohamed]

Opps :)) I'm so sorry my lady.