Ping two hosts with netmask /32.

Discussion in 'Cisco' started by wgnoevoi@gmail.com, Aug 19, 2006.

  1. Guest

    I have so simple network:


    The cisco router connect to catalyst. On catalyst is definition two
    VLAN's. There are two hosts: host_1(10.0.0.1/32) and host_2,
    (10.0.0.2/32) is connected to catalyst.
    Hosts are in different VLAN and have network mask /32 ---- it couldn't
    change. Configuration on VLAN's couldn't change too.

    Question: How I can change config on the router interface so host_1 can
    ping host_2? Is it possibility?
    , Aug 19, 2006
    #1
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  2. wrote in comp.dcom.sys.cisco:

    > I have so simple network:
    > The cisco router connect to catalyst. On catalyst is definition two
    > VLAN's. There are two hosts: host_1(10.0.0.1/32) and host_2,
    > (10.0.0.2/32) is connected to catalyst.
    > Hosts are in different VLAN and have network mask /32 ---- it couldn't
    > change. Configuration on VLAN's couldn't change too.
    > Question: How I can change config on the router interface so host_1 can
    > ping host_2? Is it possibility?


    I don't think this would work at all. If your host has a subnet mask of
    255.255.255.255 you are telling him that he is the only one in that
    subnet and since he doesn't have a default gateway he can't communicate
    with anyone else... You need to change the subnet mask.

    Note that I'm currently finishing semester 3 of CCNA classes so my
    understanding may not be correct and someone with more experience can
    correct me.
    --
    *blap*
    Danijel Starman, Aug 19, 2006
    #2
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  3. BernieM Guest

    <> wrote in message
    news:...
    >I have so simple network:
    >
    >
    > The cisco router connect to catalyst. On catalyst is definition two
    > VLAN's. There are two hosts: host_1(10.0.0.1/32) and host_2,
    > (10.0.0.2/32) is connected to catalyst.
    > Hosts are in different VLAN and have network mask /32 ---- it couldn't
    > change. Configuration on VLAN's couldn't change too.
    >
    > Question: How I can change config on the router interface so host_1 can
    > ping host_2? Is it possibility?
    >


    "/32" is not a valid network mask as it leaves no space to identify the
    network and broadcast address. What operating system has allowed you to
    apply that mask? The smallest network mask is "/30"

    What are the network addresses of the vlans that router has configured? By
    that I mean the actual 'networks' .... not hosts. .

    BernieM
    BernieM, Aug 19, 2006
    #3
  4. In article <RQCFg.14514$>,
    BernieM <> wrote:

    >"/32" is not a valid network mask as it leaves no space to identify the
    >network and broadcast address. What operating system has allowed you to
    >apply that mask? The smallest network mask is "/30"


    Correction, there is an RFC that defines /31. It is used especially
    on point-to-point links.
    Walter Roberson, Aug 19, 2006
    #4
  5. Wayne Guest

    "BernieM" <> wrote in message
    news:RQCFg.14514$...
    >
    > <> wrote in message
    > news:...
    >>I have so simple network:
    >>
    >>
    >> The cisco router connect to catalyst. On catalyst is definition two
    >> VLAN's. There are two hosts: host_1(10.0.0.1/32) and host_2,
    >> (10.0.0.2/32) is connected to catalyst.
    >> Hosts are in different VLAN and have network mask /32 ---- it couldn't
    >> change. Configuration on VLAN's couldn't change too.
    >>
    >> Question: How I can change config on the router interface so host_1 can
    >> ping host_2? Is it possibility?
    >>

    >
    > "/32" is not a valid network mask as it leaves no space to identify the
    > network and broadcast address. What operating system has allowed you to
    > apply that mask? The smallest network mask is "/30"
    >
    > What are the network addresses of the vlans that router has configured?
    > By that I mean the actual 'networks' .... not hosts. .
    >
    > BernieM
    >


    A loopback interface on a router can have a /32 mask, but that or a
    something similar would be about it.
    To the original poster, is the host in question a router, PC, other??
    Wayne, Aug 19, 2006
    #5
  6. Guest

    Wayne wrote:
    > "BernieM" <> wrote in message
    > news:RQCFg.14514$...
    > >
    > > <> wrote in message
    > > news:...
    > >>I have so simple network:
    > >>
    > >>
    > >> The cisco router connect to catalyst. On catalyst is definition two
    > >> VLAN's. There are two hosts: host_1(10.0.0.1/32) and host_2,
    > >> (10.0.0.2/32) is connected to catalyst.
    > >> Hosts are in different VLAN and have network mask /32 ---- it couldn't
    > >> change. Configuration on VLAN's couldn't change too.
    > >>
    > >> Question: How I can change config on the router interface so host_1 can
    > >> ping host_2? Is it possibility?
    > >>

    > >
    > > "/32" is not a valid network mask as it leaves no space to identify the
    > > network and broadcast address. What operating system has allowed you to
    > > apply that mask? The smallest network mask is "/30"
    > >
    > > What are the network addresses of the vlans that router has configured?
    > > By that I mean the actual 'networks' .... not hosts. .
    > >
    > > BernieM
    > >

    >
    > A loopback interface on a router can have a /32 mask, but that or a
    > something similar would be about it.
    > To the original poster, is the host in question a router, PC, other??


    It's PC.
    , Aug 19, 2006
    #6
  7. Guest

    Wayne wrote:
    > "BernieM" <> wrote in message
    > news:RQCFg.14514$...
    > >
    > > <> wrote in message
    > > news:...
    > >>I have so simple network:
    > >>
    > >>
    > >> The cisco router connect to catalyst. On catalyst is definition two
    > >> VLAN's. There are two hosts: host_1(10.0.0.1/32) and host_2,
    > >> (10.0.0.2/32) is connected to catalyst.
    > >> Hosts are in different VLAN and have network mask /32 ---- it couldn't
    > >> change. Configuration on VLAN's couldn't change too.
    > >>
    > >> Question: How I can change config on the router interface so host_1 can
    > >> ping host_2? Is it possibility?
    > >>

    > >
    > > "/32" is not a valid network mask as it leaves no space to identify the
    > > network and broadcast address. What operating system has allowed you to
    > > apply that mask? The smallest network mask is "/30"
    > >
    > > What are the network addresses of the vlans that router has configured?
    > > By that I mean the actual 'networks' .... not hosts. .
    > >
    > > BernieM
    > >

    >
    > A loopback interface on a router can have a /32 mask, but that or a
    > something similar would be about it.
    > To the original poster, is the host in question a router, PC, other??


    It's PC.
    , Aug 19, 2006
    #7
  8. Merv Guest

    and why can't the netmask be changed ?
    Merv, Aug 19, 2006
    #8
  9. On 19.08.2006 16:31 Walter Roberson wrote

    > In article <RQCFg.14514$>,
    > BernieM <> wrote:
    >
    >>"/32" is not a valid network mask as it leaves no space to identify the
    >>network and broadcast address. What operating system has allowed you to
    >>apply that mask? The smallest network mask is "/30"

    >
    > Correction, there is an RFC that defines /31. It is used especially
    > on point-to-point links.


    That's theory ... reality tells me

    gw001#sh inter loopback 0
    Loopback0 is up, line protocol is up
    Hardware is Loopback
    Internet address is 80.81.196.177/32


    --
    Arnold Nipper, AN45
    Arnold Nipper, Aug 19, 2006
    #9
  10. On 19.08.2006 17:21 wrote

    > Wayne wrote:
    >> "BernieM" <> wrote in message
    >> news:RQCFg.14514$...
    >> >
    >> > <> wrote in message
    >> > news:...
    >> >>I have so simple network:
    >> >>
    >> >>
    >> >> The cisco router connect to catalyst. On catalyst is definition two
    >> >> VLAN's. There are two hosts: host_1(10.0.0.1/32) and host_2,
    >> >> (10.0.0.2/32) is connected to catalyst.
    >> >> Hosts are in different VLAN and have network mask /32 ---- it couldn't
    >> >> change. Configuration on VLAN's couldn't change too.
    >> >>
    >> >> Question: How I can change config on the router interface so host_1 can
    >> >> ping host_2? Is it possibility?
    >> >>
    >> >
    >> > "/32" is not a valid network mask as it leaves no space to identify the
    >> > network and broadcast address. What operating system has allowed you to
    >> > apply that mask? The smallest network mask is "/30"
    >> >
    >> > What are the network addresses of the vlans that router has configured?
    >> > By that I mean the actual 'networks' .... not hosts. .
    >> >
    >> > BernieM
    >> >

    >>
    >> A loopback interface on a router can have a /32 mask, but that or a
    >> something similar would be about it.
    >> To the original poster, is the host in question a router, PC, other??

    >
    > It's PC.
    >


    And why don't you add host routes (unix slang), i.e.

    host_1: ip route add 10.0.0.2/32 dev eth0
    host_2: ip route add 10.0.0.1/32 dev eth0

    --
    Arnold Nipper, AN45
    Arnold Nipper, Aug 19, 2006
    #10
  11. In article <>,
    Arnold Nipper <> wrote:

    > And why don't you add host routes (unix slang), i.e.
    >
    > host_1: ip route add 10.0.0.2/32 dev eth0
    > host_2: ip route add 10.0.0.1/32 dev eth0


    I don't think that will work, because the hosts are in different VLANs.
    Routes like that cause the systems to ARP for each other. But since
    each VLAN is a separate broadcast domain, the ARPs will never reach each
    other.

    The only way to communicate between VLANs is via a router. The OP
    didn't mention whether his router is connected to both VLANs -- in fact,
    he didn't say how the router is connected to the switch at all.

    --
    Barry Margolin,
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***
    Barry Margolin, Aug 19, 2006
    #11
  12. BernieM Guest

    "Barry Margolin" <> wrote in message
    news:...
    > In article <>,
    > Arnold Nipper <> wrote:
    >
    >> And why don't you add host routes (unix slang), i.e.
    >>
    >> host_1: ip route add 10.0.0.2/32 dev eth0
    >> host_2: ip route add 10.0.0.1/32 dev eth0

    >
    > I don't think that will work, because the hosts are in different VLANs.
    > Routes like that cause the systems to ARP for each other. But since
    > each VLAN is a separate broadcast domain, the ARPs will never reach each
    > other.
    >
    > The only way to communicate between VLANs is via a router. The OP
    > didn't mention whether his router is connected to both VLANs -- in fact,
    > he didn't say how the router is connected to the switch at all.
    >
    > --
    > Barry Margolin,
    > Arlington, MA
    > *** PLEASE post questions in newsgroups, not directly to me ***
    > *** PLEASE don't copy me on replies, I'll read them in the group ***


    If the router is running proxy-arp the pc's hould be able to communicate.

    BernieM
    BernieM, Aug 19, 2006
    #12
  13. In article <7BLFg.14606$>,
    "BernieM" <> wrote:

    > "Barry Margolin" <> wrote in message
    > news:...
    > > In article <>,
    > > Arnold Nipper <> wrote:
    > >
    > >> And why don't you add host routes (unix slang), i.e.
    > >>
    > >> host_1: ip route add 10.0.0.2/32 dev eth0
    > >> host_2: ip route add 10.0.0.1/32 dev eth0

    > >
    > > I don't think that will work, because the hosts are in different VLANs.
    > > Routes like that cause the systems to ARP for each other. But since
    > > each VLAN is a separate broadcast domain, the ARPs will never reach each
    > > other.
    > >
    > > The only way to communicate between VLANs is via a router. The OP
    > > didn't mention whether his router is connected to both VLANs -- in fact,
    > > he didn't say how the router is connected to the switch at all.
    > >
    > > --
    > > Barry Margolin,
    > > Arlington, MA
    > > *** PLEASE post questions in newsgroups, not directly to me ***
    > > *** PLEASE don't copy me on replies, I'll read them in the group ***

    >
    > If the router is running proxy-arp the pc's hould be able to communicate.


    Only if the router is connected to both VLANs, and it has appropriate
    routing statements for the /32 addresses.

    --
    Barry Margolin,
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***
    Barry Margolin, Aug 20, 2006
    #13
  14. BernieM Guest

    "Barry Margolin" <> wrote in message
    news:...
    > In article <7BLFg.14606$>,
    > "BernieM" <> wrote:
    >
    >> "Barry Margolin" <> wrote in message
    >> news:...
    >> > In article <>,
    >> > Arnold Nipper <> wrote:
    >> >
    >> >> And why don't you add host routes (unix slang), i.e.
    >> >>
    >> >> host_1: ip route add 10.0.0.2/32 dev eth0
    >> >> host_2: ip route add 10.0.0.1/32 dev eth0
    >> >
    >> > I don't think that will work, because the hosts are in different VLANs.
    >> > Routes like that cause the systems to ARP for each other. But since
    >> > each VLAN is a separate broadcast domain, the ARPs will never reach
    >> > each
    >> > other.
    >> >
    >> > The only way to communicate between VLANs is via a router. The OP
    >> > didn't mention whether his router is connected to both VLANs -- in
    >> > fact,
    >> > he didn't say how the router is connected to the switch at all.
    >> >
    >> > --
    >> > Barry Margolin,
    >> > Arlington, MA
    >> > *** PLEASE post questions in newsgroups, not directly to me ***
    >> > *** PLEASE don't copy me on replies, I'll read them in the group ***

    >>
    >> If the router is running proxy-arp the pc's hould be able to communicate.

    >
    > Only if the router is connected to both VLANs, and it has appropriate
    > routing statements for the /32 addresses.
    >
    > --
    > Barry Margolin,


    yes, and as long as there are no restrictions in place ie. acls' etc. The
    original poster doesn't indicate the extent to which they have access to
    this type of info.

    BernieM
    BernieM, Aug 20, 2006
    #14
  15. Walter Roberson wrote:
    > Correction, there is an RFC that defines /31. It is used especially
    > on point-to-point links.


    RFC number please? :)

    Usually in ptp links, ip-addresing scheme took /30 that leaves 4 ip
    addresses 1 for network, 2 for end-point ip, and 1 for broadcast.

    --
    thx
    David Sudjiman

    http://www.davidsudjiman.info
    David Sudjiman, Aug 20, 2006
    #15
  16. Arnold Nipper wrote:
    > gw001#sh inter loopback 0
    > Loopback0 is up, line protocol is up
    > Hardware is Loopback
    > Internet address is 80.81.196.177/32


    Yes, this loopback addr can use /32 addressing. But it is only for
    redistributing/routing update only. It is a different case.

    --
    thx
    David Sudjiman

    http://www.davidsudjiman.info
    David Sudjiman, Aug 20, 2006
    #16
  17. In article <zD5Gg.15184$>,
    David Sudjiman <> wrote:
    >Walter Roberson wrote:
    >> Correction, there is an RFC that defines /31. It is used especially
    >> on point-to-point links.


    >RFC number please? :)


    >Usually in ptp links, ip-addresing scheme took /30 that leaves 4 ip
    >addresses 1 for network, 2 for end-point ip, and 1 for broadcast.


    RFC 3021 "Using 31-Bit Prefixes on IPv4 Point-to-Point links"
    Walter Roberson, Aug 20, 2006
    #17
  18. Guest

    Walter Roberson wrote:
    > In article <zD5Gg.15184$>,
    > David Sudjiman <> wrote:
    > >Walter Roberson wrote:
    > >> Correction, there is an RFC that defines /31. It is used especially
    > >> on point-to-point links.

    >
    > >RFC number please? :)

    >
    > >Usually in ptp links, ip-addresing scheme took /30 that leaves 4 ip
    > >addresses 1 for network, 2 for end-point ip, and 1 for broadcast.

    >
    > RFC 3021 "Using 31-Bit Prefixes on IPv4 Point-to-Point links"


    Thank's everybody.
    It schema wasn't work, i.e. /32 is netmask without host. So for "live"
    interface in CORRECTLY work OS we couldn't config this mask. Because
    this mask contradict exist of interfaces. Another history with
    loopback, i.e. it is emulations networks without host.
    , Aug 21, 2006
    #18
  19. Guest

    wrote:
    > Walter Roberson wrote:
    > > In article <zD5Gg.15184$>,
    > > David Sudjiman <> wrote:
    > > >Walter Roberson wrote:
    > > >> Correction, there is an RFC that defines /31. It is used especially
    > > >> on point-to-point links.

    > >
    > > >RFC number please? :)

    > >
    > > >Usually in ptp links, ip-addresing scheme took /30 that leaves 4 ip
    > > >addresses 1 for network, 2 for end-point ip, and 1 for broadcast.

    > >
    > > RFC 3021 "Using 31-Bit Prefixes on IPv4 Point-to-Point links"

    >
    > Thank's everybody.
    > It schema wasn't work, i.e. /32 is netmask without host. So for "live"
    > interface in CORRECTLY work OS we couldn't config this mask. Because
    > this mask contradict exist of interfaces. Another history with
    > loopback, i.e. it is emulations networks without host.


    All that I sad before --- folly. Question is unsolvable.
    , Aug 21, 2006
    #19
  20. BernieM Guest

    <> wrote in message
    news:...
    >
    > wrote:
    >> Walter Roberson wrote:
    >> > In article <zD5Gg.15184$>,
    >> > David Sudjiman <> wrote:
    >> > >Walter Roberson wrote:
    >> > >> Correction, there is an RFC that defines /31. It is used especially
    >> > >> on point-to-point links.
    >> >
    >> > >RFC number please? :)
    >> >
    >> > >Usually in ptp links, ip-addresing scheme took /30 that leaves 4 ip
    >> > >addresses 1 for network, 2 for end-point ip, and 1 for broadcast.
    >> >
    >> > RFC 3021 "Using 31-Bit Prefixes on IPv4 Point-to-Point links"

    >>
    >> Thank's everybody.
    >> It schema wasn't work, i.e. /32 is netmask without host. So for "live"
    >> interface in CORRECTLY work OS we couldn't config this mask. Because
    >> this mask contradict exist of interfaces. Another history with
    >> loopback, i.e. it is emulations networks without host.

    >
    > All that I sad before --- folly. Question is unsolvable.
    >


    If the interface is more or less a loopback then you're right .. it's
    unsolvable. It's the same as configuring a "127.x.x.x" address. It doesn't
    matter what mask you use and how many hosts are in the same vlan configured
    this way .... they're never going to talk ... packet are never going to even
    hit the wire.

    BernieM
    BernieM, Aug 21, 2006
    #20
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