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  • Connecting 1 router to another

    i am using a cisco asa 5510 that gives out dhcp connected to a switch. if i come out the switch, and connect to a linksys WAN SIDE using get ip address automatically, connect LAN side to a computer, i get a address from the linksys, but i don't get the internet.......How do i fix that, and why does it not work.

    i know if i turn off enable dhcp on the linksys, and connect only to the lan side, that i will get an address from the cisco, and will work, but i don't want that.


    Thanks
    Last edited by Kobe 310; 16th January 2013, 21:04.

  • #2
    Re: Connecting 1 router to another

    The question is why would you want to put a Linksys behind the ASA? Do you have nat configured on the ASA? Do you have a default route configured on the ASA for the ISP upstream router? The ASA dhcp server pool must be on the same subnet as the interface the dhcp server is enabled on as well. (Example - If the ASA inside interface is on the 192.168.2.0/24 network then the dhcp pool must be part of the 192.168.2.0 network) This is a limitation of dhcp on the ASA. With Cisco IOS routers this isn't an issue) In short the ASA can't assign dhcp addresses for remote networks.

    Does the WAN interface of the linksys get an ip address via dhcp from the ASA? It should if they are on the same Layer 2 segment. What ip addressing are you assigning to the "inside" interface of the Linksys? Is nat enabled on the linksys as well? Don't know with the default software if you can even disable nat. (I know with 3rd party code you can - Tomato etc...)

    The linksys is very limited in configuration compared to business class devices. The big question is why you would want to do this and what is your goal.
    Last edited by auglan; 16th January 2013, 22:12.
    CCNA, CCNA-Security, CCNP
    CCIE Security (In Progress)

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    • #3
      Re: Connecting 1 router to another

      the main reason was just to lean. I figure if i could get that to work it would improve my networking understanding. i'm usually given advise to read books.May sound silly, but i'm not good at all at reading or understanding books. For me it's a waste of time unfortunately.

      I love to learn new things, and again unfortunately it's always the long hard way. But worth it!!!!!!!

      I have a few asa's set up, this particular one is in a test enviroment. i wanted to set up a wireless network, gettiing ip from asa(which is does), and giving diffrent inside address. I know i could use a diffrent interface to accpmplish this, just want to do it this way.

      asa inside is 10.1.25.0/24 linksys gets address of 10.1.25.101. linksys gives out 192.168.50.1.

      i thought it may be difficult, but now that i think about it, i thought if the asa gives an address, that the nat is created automatically, just as if you connected a comcast modem to a linksys router, you don't have to do anything, its ready to go
      Last edited by Kobe 310; 17th January 2013, 15:57.

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      • #4
        Re: Connecting 1 router to another

        There is no default config on the ASA for nat or pretty much anything else. Its a business/enterprise device so they leave the options up to you. Its good to learn on real equipment as you get good exposure to any potential issues that come up. I would not recommend using a linksys device though as they don 't have the configuration options that an ASA or Cisco IOS router would have.

        Check out GNS3 if your interested in learning Cisco, Juniper etc. Its an emulator (not a simulator) as it runs actual ASA and IOS code without spending the cash on real equipment. You can run the newer ASA code 8.4 on it as well. You do need a valid cisco login to download the IOS etc...


        In your case you would being doing a double nat as the linksys will nat to a different private ip space and the ASA would nat to a routable public address.


        http://www.gns3.org/


        Also check out Keith Barker's youtube channel as well as his videos on CBT Nuggets. He is a great teach with a lot of knowledge

        http://www.youtube.com/user/Keith6783
        Last edited by auglan; 17th January 2013, 19:49.
        CCNA, CCNA-Security, CCNP
        CCIE Security (In Progress)

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        • #5
          Re: Connecting 1 router to another

          greatly appreciated, thank you!!!

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