secure remote access and firewalls

From: Colin Horsington (c.horsingtonat_private)
Date: Tue Oct 26 1999 - 17:04:19 PDT

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    Dear Firewall-users
    
    Recently their has been a requirement to link up securely some remote
    branches. To do this it has been proposed to use firewalls not to do VPN in
    the strict sense of the word, but to implement packet filtering effects to
    limit access to the remote machines.
    
    For example let's say branch A wishes for branch B to see computer X. Both
    branch A and B have firewalls. Branch A places (or using NAT gives) computer
    a real IP outside the branch A's firewall. But since anyone can now access
    this real IP, an upstream packet filter (firewall) is placed amid the
    traffic stream. Effectively blocking (using rules) anyone accessing
    restricted real IP addresses down stream (ie at branch A). Similiarly branch
    B would use the same methodolgy.
    
    This schema is replicated for upto 4 branches that wish to restrict access
    to particular computers and the internet in general without comprimising
    security to much.
    
    -------------------       -----------------        -----------------
    ------------------------------
    -----------------------------------------
    | Branch A   |-------| Firewall A |--------| real IP's  |----------------|
    Firewall B filtering  |----------------------| Internet -> other branches |
    -------------------       -----------------        -----------------
    ------------------------------
    -----------------------------------------
    
    Does this have any security implications besides un-encrypted packets
    travelling over the public network. If so what other methods could be used
    considering every branch does not want to change it's current infrastrucure
    much, and does not want to have to use a specific firewall for firewall A
    nor chnage what they have, and firewall B may also be a different box at
    every location!
    
    Also if a 'VPN' were to be used how could one be setup between all branches
    as one vpn, rather than having nxn (n squared) vpn's.
    
    Kind regards,
    
    Colin Horsington
    



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