[HLUG] Mixing CAT5 and CAT6

[Richard Leszczynski]

Traffic between two devices on a network will only be able to move as
fast as the slowest component on the route between the two devices.
The components in question being the PCs' NICs, the cabling and any
hubs or switches or routers on a direct path between the PCs.

The different UTP cabling standards call for cables bearing their name
to carry data at a specified rate to a specified maximum distance.

CAT3 should carry data at 10Mbps over a maximum distance of 100m
CAT5 carries data at 100Mbps over 100m
CAT5e carries data at 1Gbps over 100m
CAT6 carries data at 10Gbps over only 55m although this reduction in
distance is unlikely to be an issue in domestic LANs unless you're
thinking of building a data centre in the shed at the end of your
garden.
CAT6a still carries data at 10Gbps but restores the transmission
distance to 100m

and CAT6e is not actually a standard but a marketing name so means
different things to different cable manufacturers, but they generally
applied the moniker to cables supposed to offer some benefit over
CAT5e.

That said, a shorter run of an inferior cable, for example 20m of
CAT5, might be able to support the higher CAT5e data rate of 1Gbps if
used to connect two PCs with 1Gb NICs but YMMV and it depends on
individual circumstances.

The sort of LAN you describe - fast office and slower guest rooms - is
achievable using a couple of different switches and two star topology
networks linked together.

For the fast office part, you'll need a 1GBps switch at the centre of
the office star and all cabling to each machine connected to that
switch must be Cat5e or better. Each PC connected to that switch
should have a 1Gb NIC for maximum benefit. If a PC connected to that
switch only has a 10/100Mbps NIC, then it won't slow everything on the
star down, only its own communications with any other machine on the
LAN will be limited.

ASIDE: It can be argued that on a star topology network that connects
multiple user workstations and a single server together, only the
switch and server should have 1Gbps connection and all clients should
be limited to 100Mbps connections in a crude but effective way of
preventing any single client being able to hog the server's entire
1Gbps bandwidth at any one time. This limitation would usually be
implemented in software, rather than done by downgrading hardware as
1Gbps NICs tend to be ubiquitous built-in components on motherboards
nowadays. This more of an issue in a proper office environment with
multiple users continuously accessing server resources simultaneously,
rather than on a smaller domestic LAN.

For the slow guest rooms part, you can use one of your legacy Linksys
10/100Mbps hubs/switches as the centre of the guest star and cabling
to each PC connected to this old switch doesn't have to be anything
better than the old CAT5 standard. The maximum speed that any PC
connected to this old switch will be able to communicate with any
other PC on the LAN will is the 100Mbps of the old switch.

The switch at the centre of the guest star can be connected to the the
switch at the centre of the office star with CAT5 cable. However some
old 10/100Mbps switches came with a single 1Gbps port for uplink, and
if your old Linksys has this feature, then use this single 1Gbps port
to connect it to the office switch with CAT5e cable or better.

Another note. your new CAT6 cabling supports 10Gbps but it is unlikely
you'll be able to use it to its full potential for a few years as 10Gb
NICs and switches are still both very rare and very expensive in the
consumer environment.

hope this helps.
Richard


On 9 June 2017 at 13:22, Julian Robbins via Herefordshire
<herefordshire at mailman.lug.org.uk> wrote:
> Hi George
>
> Broadly yes ..
>
> We used to have parallel networks with a cat 6 backbone at work a good
> number of years ago.  And yes using cat 5 cables and routers will slow the
> cat 6 traffic down. So choose your network topology carefully and you can
> make best use of what you have .
>
> Julian
>
> On 9 Jun 2017 12:00 p.m., "George DiceGeorge via Herefordshire" <
> herefordshire at mailman.lug.org.uk> wrote:
>
>> I have a lot of old CAT5 ethernet wires and routers,
>> but just ordered some CAT6 which is faster.
>>
>> I've read somewhere that networks slow down to the speed of the slowest
>> link.
>>
>> How can I mix them?
>> If I use old Linksys  10/100 routers will it slow everything else down?
>>
>> Could I have a slow network going to far away rooms for guests
>> and a fast one around my office?
>>
>> george
>>
>>
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