ethernet, making cables - what am I doing wrong?

comp.dcom.lans.ethernet - Discussions of the Ethernet/IEEE 802.3 protocols.


ethernet >> making cables - what am I doing wrong?

by meshko » Mon, 03 Apr 2006 10:21:41 GMT

I'm making ethernet cables which don't quite work and it's drivign me
crazy.
I can't quite explain under what conditions they work and don't work.
It seems that they do work with almost all (or juts all) 10 mbit boards
but don't work with the newer 100mbit boards. I've used two different
sources of cat 5e cable, in one case it's not clerly labeled for speed,
in the other it says that it was tested for Gigabit networks. Results
are the same. So it must be the heads I'm using? Is this even
possible? Or could it be the crimper? Because I've tried heads from
two different sources -- doesn't seem to make a difference.
When I plug such cable between a 100mbit Linksys router and a 100mbit
PCMCIA card the light on the switch goes on for couple of seconds,
blinking very-very fast and then disappears. If I replace the PCMCIA
card with an old one 10mbit card it works fine.
Please help, I'm getting scared.

Top

ethernet >> making cables - what am I doing wrong?

by Dale Farmer » Mon, 03 Apr 2006 11:45:26 GMT



You are probably untwisting the pairs too much. the twist of the
pairs needs to be maintained right up until the last millimeter. Also
possible you are using connectors designed for stranded wire with solid
wire, or vice versa. If you are making patch cables, I submit that you
can buy them for far less money from various online sources than what
your time and materials are costing you.

--Dale
Top

ethernet >> making cables - what am I doing wrong?

by William P.N. Smith » Mon, 03 Apr 2006 12:16:53 GMT


How are you building the cables? Sounds like a classic case of not
building them to 568A or B...

http://www.tomsnetworking.com/network/20030630/images/568a.jpg
Top

ethernet >> making cables - what am I doing wrong?

by glen herrmannsfeldt » Mon, 03 Apr 2006 15:30:21 GMT


(snip)


It is much more likely mispairing. The untwist requirement for
100baseTX isn't quite that bad. Cat5 is supposed to be good enough for
gigabit, but even gigabit won't be that sensitive until you are close to
the maximum length. I thought the Cat5 spec. was closer to 0.5in, or
about 12mm. 100baseTX will likely work with significantly more, and
10baseT even more than that.

Mispairing means that the two wires used by a signal aren't a twisted
pair. For 10baseT and 100baseTX ethernet the pairs are (1,2) and (3,6).
Normally ethernet cables are wired with (1,2), (3,6), (4,5), and (7,8)
as twisted pairs as required for gigabit. If you didn't do that, then
that is the problem. A mispaired cable will work to about 10m on
10baseT and about 1m on 100baseTX (depending on which pairs you actually
use it could be more or less). (And probably about 0.1m for gigabit.)

-- glen
Top

ethernet >> making cables - what am I doing wrong?

by info_at_telecom-gear_dot_com » Mon, 03 Apr 2006 21:46:46 GMT


The cables you are using should get you 1Gbit/s no problem. Sounds like
you might be making a straight-through cable without actually placing all
conductors into their standard-defined positions. Check your color code
with either T568A or T568B pinouts:
http://www.cabling-design.com/references/pinouts/t568ab.shtml
and make sure you use the same pinout on both ends of the cable. One other
thing: very often people use heads designed for stranded cable on a solid
conductor one. This usually results in higher attenuation, but could
actually have other symptoms as well. Check with the supplier of your
plugs - make sure you are using the correct type for your cable.



Cheers!
Dmitriy

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Top

ethernet >> making cables - what am I doing wrong?

by meshko » Mon, 03 Apr 2006 21:50:14 GMT

Yes, you are right. I wasn't doing it according to the spec. I didn't
realize that the pair that was used had to be tweasted and that that
pair wasn't consequtive (3,6). Very, very stupid of me. Thank you
very much for getting me straight.
Top
Similar Threads

1. Object tracking - What am i doing wrong? 

Hi all,

I have been trying to get an ISDN circuit to dial up and connect 2x 1841 
Cisco routers together if the primary adsl interface fails.


Backgroud:
Main site: 192.168.1.x
Remote Site: 192.168.2.x
VPN to each end over aDSL appears to work fine, no reported issues (not sure 
its 100% correct, but it works).

Due to an issue with the DSL connection at the remote site, it has been 
decided to introduce an ISDN circuit at each end, so if the dsl fails, then 
the sites can connect via ISDN.

ISDN calls must be made from the MAIN site to the remote site.

After asking on this group the other day, it was suggested that the 
backup-interface doesnt work that well, and some sort of route object 
tracking was needed to perform the fuction correctly.

This is what i have tried to do however its not working I'm sure its only an 
access list that is stopping the ISDN dialing up, but I'm not seeing my 
mistake at the moment! Can you?

------------------------------------------------------------------------------------------------------

Configuration from Main site (any boring stuff edited out)
aaa new-model
aaa authentication login default local
aaa authentication ppp default local
!
ip sla monitor 1
 type echo protocol ipIcmpEcho (ADSL outside interface at remote site)
ip sla monitor schedule 1 life forever start-time now
!
isdn switch-type basic-net3
!
crypto pki trustpoint TP-self-signed-30453xxxxxx
!
!
crypto pki certificate chain TP-self-signed-30453xxxxxx
!
username admin privilege 15 secret
username backup password 7
!
!
track 123 rtr 1 reachability
!
!
crypto isakmp policy 1
 encr 3des
 authentication pre-share
 group 2
crypto isakmp key  xxxxxxxx address (ADSL outside interface at remote site)
!
!
crypto ipsec transform-set ESP-3DES-SHA esp-3des esp-sha-hmac
!
crypto map SDM_CMAP_1 1 ipsec-isakmp
 set peer (ADSL outside interface at remote site)
 set transform-set ESP-3DES-SHA
 match address 100
!
!
!
interface FastEthernet0/0
 ip address 192.168.1.242 255.255.255.0
 ip nat inside
 ip virtual-reassembly
 duplex auto
 speed auto
!
interface ATM0/0/0
 no ip address
 no atm ilmi-keepalive
 dsl operating-mode auto
!
interface ATM0/0/0.1 point-to-point
 pvc 0/38
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
 !
!
interface BRI0/1/0
 no ip address
 encapsulation ppp
 dialer pool-member 2
 isdn switch-type basic-net3
 isdn point-to-point-setup
 ppp authentication chap
!
interface Dialer0
 ip address negotiated
 ip nat outside
 ip virtual-reassembly
encapsulation ppp
 dialer pool 1
 dialer-group 1
 ppp authentication chap callin
 ppp chap hostname  XXXX@XXXXX.COM 
 ppp chap password 7
 crypto map SDM_CMAP_1
!
interface Dialer2
 ip address 172.16.200.2 255.255.255.0
 encapsulation ppp
 dialer pool 2
 dialer idle-timeout 180
 dialer string (remote site number)
 dialer-group 2
 ppp chap hostname backup
 ppp chap password 7 (same as password defined above)
!
ip local policy route-map MY_Backup_Policy
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer0 track 123
ip route 0.0.0.0 0.0.0.0 Dialer2 100
!
access-list 1 permit 192.168.1.0 0.0.0.255
access-list 100 permit ip 192.168.1.0 0.0.0.255 192.168.2.0 0.0.0.255
access-list 101 deny   ip 192.168.1.0 0.0.0.255 192.168.2.0 0.0.0.255
access-list 101 permit ip 192.168.1.0 0.0.0.255 any
access-list 105 permit icmp any host 80.229.86.228 echo
dialer-list 1 protocol ip permit
dialer-list 2 protocol ip permit
route-map MY_Backup_Policy permit 10
 match ip address 105
 set interface Null0
 set ip next-hop (outside interface of this router when connected to adsl)
!
route-map SDM_RMAP_1 permit 1
 match ip address 101
!
end

------------------------------------------------------------------------------------------------------

Remote site (remember this just needs to answer the isdn calls from main 
site)

aaa new-model
aaa authentication login default local
aaa authentication ppp default local
!
isdn switch-type basic-net3
!
crypto pki trustpoint TP-self-signed-214962xxxx
 enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-214962xxxx
 revocation-check none
 rsakeypair TP-self-signed-214962xxxx
!
!
crypto pki certificate chain TP-self-signed-214962xxxx
 certificate self-signed 01
!
username admin privilege 15 xxxxxxxxxxxx
username backup password 7 xxxxxxxxxx
!

crypto isakmp policy 1
 encr 3des
 authentication pre-share
 group 2
crypto isakmp key xxxxxxxxxxx address (main site outside interface)
!
!
crypto ipsec transform-set ESP-3DES-SHA esp-3des esp-sha-hmac
!
crypto map SDM_CMAP_1 1 ipsec-isakmp
 description Tunnel to80.229.44.16
 set peer (main site outside interface)
 set transform-set ESP-3DES-SHA
 match address 100
!
interface FastEthernet0/0
 ip address 192.168.2.254 255.255.255.0
 ip nat inside
 ip virtual-reassembly
 duplex auto
 speed auto
!
interface ATM0/0/0
 no ip address
 no atm ilmi-keepalive
 dsl operating-mode auto
!
interface ATM0/0/0.1 point-to-point
 pvc 0/38
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
 !
!
interface BRI0/1/0
 no ip address
 isdn switch-type basic-net3
 isdn point-to-point-setup
!
interface Dialer0
 ip address negotiated
 ip nat outside
 ip virtual-reassembly
 encapsulation ppp
 dialer pool 1
 dialer-group 1
 ppp authentication chap callin
 ppp chap hostname  XXXX@XXXXX.COM 
 ppp chap password 7
 crypto map SDM_CMAP_1
!
interface Dialer2
 ip address 172.16.200.2 255.255.255.0
 encapsulation ppp
 dialer pool 2
 dialer-group 2
 ppp chap hostname backup
 ppp chap password 7 (same as password defined above)
!
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer0
ip route 0.0.0.0 0.0.0.0 Dialer2 100
!
ip nat inside source route-map SDM_RMAP_1 interface Dialer0 overload
!
access-list 1 permit 192.168.2.0 0.0.0.255
access-list 100 permit ip 192.168.2.0 0.0.0.255 192.168.1.0 0.0.0.255
access-list 101 deny   ip 192.168.2.0 0.0.0.255 192.168.1.0 0.0.0.255
access-list 101 permit ip 192.168.2.0 0.0.0.255 any
dialer-list 1 protocol ip permit
dialer-list 2 protocol ip permit
route-map SDM_RMAP_1 permit 1
 match ip address 101
!
end

------------------------------------------------------------------------------------------------------





To show that tracking is working correctly on the MAIN unit, you can see the 
following:

#sho track
Track 123
  Response Time Reporter 1 reachability
  Reachability is Up
    1 change, last change 00:00:26
  Latest operation return code: OK
  Latest RTT (millisecs) 52
  Tracked by:
    STATIC-IP-ROUTING 0

#sho ip rout
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static 
route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 0.0.0.0 to network 0.0.0.0

     80.0.0.0/32 is subnetted, 1 subnets
C       (outside interface of this router) is directly connected, Dialer0
     172.16.0.0/24 is subnetted, 1 subnets
C       172.16.200.0 is directly connected, Dialer2
     195.166.128.0/32 is subnetted, 1 subnets   <-ISP kit
C       195.166.128.123 is directly connected, Dialer0  <-ISP kit
C    192.168.1.0/24 is directly connected, FastEthernet0/0
S*   0.0.0.0/0 is directly connected, Dialer0

#show ip route track-table
 ip route 0.0.0.0 0.0.0.0 Dialer0 track 123 state is [up]

------------------------------------------------------------------------------------------------------

Congtratulations if you have got this far, thanks for taking the time to 
read and a triple thanks! if you are able to point out the errors in my way.

Kindest regards

Bob

p.s.
I hope I haven't scared anyone of, I ideally would like to keep this here 
(google groups will cache it) so that others can gain information from it 
(i'm sure dsl with isdn backup is required by a few people at least! so a 
working soultion i'm sure would be welcome)

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-- 
Please use my first and last name in the address & remove '.invalid'
Mijn voor- en achternaam gebruiken in het adres zonder '.invalid'

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