07-15-2003 10:25 PM - edited 03-02-2019 08:53 AM
Our Core (6509) switch is configured for a VLAN network...At present there are about 15 VLANs configured...My particular interest is in the broadcast ip (ex. 172.x.x.255) everytime I Ping these Ip address using ms dos prompt from the P.C., it is replying. the next interesting thing to happened is when you telnet the broadcast ip (172.x.x.255) the core switch (6509) answer...
Any idea
07-15-2003 10:41 PM
Hi,
AFAIK,
1) if you ping to a broadcast address (172.x.x.255) each station in the subnet has to respond. Some ping implementations do show the real IP address of the responder, some (MS Windows, e.g.) don't.
2) Just guessing: Are you connected directly to the core switch which has it's IP address in 172.x.x.0/24 subnet? If yes, try to connect to through another switch which also fulfills this address condition and maybe it will catch the telnet session now.
Regards,
Milan
07-16-2003 02:25 AM
yes I am directly connected to the core switch I tried to use a switch in between the core switch and my vlan network which had the address of 172.16.vlan.x/24 the problem still the same, "whenever I telnet the broadcast IP which is 172.16.vlan.255" the core switch answer to my telnet request.
07-16-2003 04:19 AM
Hi,
additional questions:
1) Is the core switch configured as pure L2 switch or does it provide some L3 functionality?
2) Is the PC you are Telnetting from also in the 172.16.vlan.255 subnet?
3) Is the core switch address configured as the default gateway on the PC?
I can't imagine PC Telnetting to the broadcast address in it's subnet. But if the PC is in another subnet it might send the Telnet frame to the default gateway.
My idea is the core switch is providing some proxy functions on L3.
Regards,
Milan
07-16-2003 04:33 PM
Hello,
Yes the core switch provide L3 functionality,
The PC where im telnetting is from VLAN6,(its add. 172.x.VLAN6.x).
The core switch is the default gateway of for the PC.
Yes you are right, The PC could not telnet the broadcast address from its own Vlan. if the PC belong to vlan 6 and its ip address is 172.x.vlan6.x, it could not telnet the broadcast ip on vlan 6 which is 172.x.vlan6.255, However it can telnet the broadcast ip from other vlan (ex. 172.x.vlan3.255).
if the Core switch is providing some proxy functions on L3. Do you have any idea or work around on this?
07-16-2003 11:28 PM
Hi,
it's difficult without knowing the core switch config. Is it running IOS or CatOS?
Can you provide the L3 config part? Especially the VLAN interfaces or subinterfaces config?
Just one blind shot:
If running IOS, is no ip directed-broadcast command used?
Regards,
Milan
07-17-2003 12:28 AM
Hi,
Im attaching the L3 config for you to see,
The statement no ip directed is already added to the interface however, I notice that there's no effect and does not resolve the issue.
hostname MSFC2_Core
!
boot system bootflash:c6msfc2-dsv-mz.121-11b.E.bin
boot bootldr bootflash:c6msfc2-boot-mz.121-11b.E.bin
ip subnet-zero
!
ipx routing 00d0.005e.4bfc
mls rp nde-address 172.xx.xx.xxx
mls rp ip
no mls ip multicast aggregate
!
!
!
interface Vlan1
ip address 172.xx.xx.xxx 255.255.240.0
mls rp management-interface
mls rp ip
!
interface Vlan2
ip address 172.xx.Vlan2.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan3
ip address 172.xx.Vlan3.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan4
ip address 172.xx.Vlan4.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan5
ip address 172.xx.Vlan5.xx 255.255.255.0
mls rp vtp-domain
mls rp ip
!
interface Vlan6
ip address 172.xx.Vlan6.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan7
ip address 172.xx.Vlan7.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan8
ip address 172.xx.VLAN8.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan9
ip address 172.xx.Vlan9.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan10
ip address 172.xx.Vlan10.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
!
interface Vlan14
ip address 172.xx.Vlan14.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan15
ip address 172.xx.Vlan15.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan32
ip address 172.xx.Vlan32.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan33
ip address 172.xx.Vlan33.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan34
ip address 172.xx.Vlan34.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
interface Vlan40
ip address 172.xx.Vlan40.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp ip
!
interface Vlan41
ip address 172.xx.xx.xx 255.255.255.0
ip helper-address 172.xx.xx.xxx
mls rp vtp-domain
mls rp ip
!
router ospf 1
log-adjacency-changes
network 172.xx.Vlan2.0 0.0.0.255 area 0
network 172.xx.Vlan3.0 0.0.0.255 area 0
network 172.xx.Vlan4.0 0.0.0.255 area 0
network 172.xx.Vlan5.0 0.0.0.255 area 0
network 172.xx.Vlan6.0 0.0.0.255 area 0
network 172.xx.Vlan7.0 0.0.0.255 area 0
network 172.xx.Vlan8.0 0.0.0.255 area 0
network 172.xx.Vlan9.0 0.0.0.255 area 0
network 172.xx.Vlan10.0 0.0.0.255 area 0
network 172.xx.Vlan11.0 0.0.0.255 area 0
network 172.xx.Vlan12.0 0.0.0.255 area 0
network 172.xx.Vlan13.0 0.0.0.255 area 0
network 172.xx.Vlan14.0 0.0.0.255 area 0
network 172.xx.Vlan15.0 0.0.0.255 area 0
network 172.xx.Vlan16.0 0.0.15.255 area 0
network 172.xx.Vlan32.0 0.0.0.255 area 0
network 172.xx.Vlan33.0 0.0.0.255 area 0
network 172.xx.Vlan34.0 0.0.0.255 area 0
network 172.xx.Vlan40.0 0.0.0.255 area 0
network 172.xx.Vlan41.0 0.0.0.255 area 0
!
line con 0
line vty 0 4
password
login
!
end
07-17-2003 06:14 AM
Hi,
I don't see anything wrong in the config.
To clarify:
IP helper-address specifies your DHCP server address in VLAN5?
What is the source and target VLAN when you are Telnetting?
Regards,
Milan
07-17-2003 04:35 PM
Yes I also add Ip helper address in Vlan5...
The source Vlan is in Vlan6 where my pc is connected the target Vlan when telnetting is any other vlan (i can telnet 172.xx.Vlan3.255 or 172.xx.Vlan4.255) and so on...
07-18-2003 12:38 AM
Well, I've got no new ideas.
Last low-chance try:
Remove ip helper-address from int VLAN6 (or try to connect from VLAN5 without adding ip helper-address).
(There might be something incorrect in it.)
Regards,
Milan
07-18-2003 01:27 AM
Thanks Milan,
I remove the ip helper address statement but still didn't work.
Regards,
Leo
07-18-2003 01:48 AM
Leo,
I really don't know what to try next. Maybe the mls commands...
Or try to open a TAC case.
If you provide them the complete config and IOS version, they should know.
Regards,
Milan
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