[sdnog] Force client to use HTTP proxy

Nishal Goburdhan nishal at controlfreak.co.za
Mon Jan 14 16:36:40 SAST 2019

On 12 Jan 2019, at 1:08, Kabantsh Alameen wrote:

> i've already done that (having two interfaces one for traffic and the 
> other
> for management each is separate VLAN ).
> Why ?? this proxy i am using is supporting both HTTP and HTTPS.
> in my case i have no other solution.
> Thank you very much and i will do my research on the tool that you 
> gave to
> me.

what i meant, was that you want to have one interface for incoming (from 
your network) traffic;  ie.  pre-wccp-inspect, and another for 
sorry, i wrote that badly, so let me try to explain.  it’s been a 
while since i had to do this, but wccp is applied on an interface.  so 
basically, you’d want something like:
your network  -> internal gateway -> wccp inspect sends this to cache 
farm on a different vlan -> cache-farm sends it to external router 
(using cache’s SRC_IP) -> router to internet … etc.
and the return packet, which is now destined for your cache’s IP 
address will go:
internet -> border router -> cache farm -> cache looks up who the 
original request came from -> internal router -> your network
so, your cache-farm becomes a “service vlan” off onto one side of 
your network.  if something happens to the cache-farm, disable wccp, and 
everything passes straight to the internet.  no mucking around with 
client machines, changing proxies, etc.

on a cisco, it (used to be) best to apply this _inbound_ to an 
interface, because that means that the router will “touch” the 
packet for operations fewer times.  i guess it largely depends on your 

caching https is trickier.  it’s technically encrypted, so if you want 
to cache this, you’re going to have to decrypt and re-encrypt.  
that’s certainly possible today  :-)  but there’s a larger question 
about whether it’s ethical, or not.
for example, to cache https://www.example.com, you’d have to pretend 
that your cache is actually www.example.com;  that’s effectively a 
man-in-the-middle attack.  you might get away with this, at a corporate, 
where it’s the policy that “anything done on a work computer is 
liable to be inspected by the IT director”  but at an ISP .. well, 
that’s not something that’s going to cause your customers to trust 
example.com is innocuous;  what if you tried to cache my internet 

your choice - either way, whatever you do, make sure you have a policy 
to support it.

On 12 Jan 2019, at 1:12, Kabantsh Alameen wrote:

> And if i need to scale horizontally i will configure an HTTP/HTTPS 
> load
> balancer such as HAProxy using my current IP as a virtual IP for the 
> load
> balancer.
> Thank you again for your help. 😍

no, there’s no need for a load-balancer.
the router(s) and cache(s) sets up identifiers between themselves, so 
you can have multiple caches performing with multiple routers (because, 
you want redundancy, right?).  i _think_ the caveat was that they needed 
to be in the same network for each service (ie. web-caches would be in 
one vlan;  ftp-caches in another, etc).  but honestly, it’s been a 
decade since i last had to play with this, so you’re actually better 
off searching for what your hardware can support, and testing this out.  
wccp is an ietf standard, so although there might be some vendor 
uniqueness, it should Just Work.  if you run into problems, feel free to 
ask on-list.


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