Configuración de la intercepción TCP en los routers Cisco IOS/IOS-XE

Introducción

Este documento describe los requisitos para habilitar la función de intercepción del protocolo de control de transmisión (TCP) de Cisco en los routers Cisco IOS®/IOS-XE. La intercepción TCP es necesaria para proteger los servidores TCP de ataques de inundación TCP (SYN), un tipo de ataque de denegación de servicio.

Prerequisites

Requirements

No hay requisitos específicos para este documento.

Componentes Utilizados

Este documento no tiene restricciones específicas en cuanto a versiones de software y de hardware.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. Si tiene una red en vivo, asegúrese de entender el posible impacto de cualquier comando.

Problema

No puede configurar 'ip tcp intercept' en los routers ISR G1/G2/G3 y ASR1k. Puede ver los registros aquí:

• Para routers ISR G1

Router#show ver

Cisco IOS® Software, 2800 Software (C2800NM-IPBASEK9-M), Version 15.1(4)M12a, RELEASE SOFTWARE (fc1)
Router uptime is 14 minutes
System returned to ROM by reload at 07:45:56 UTC Tue Nov 1 2016
System image file is "flash:c2800nm-ipbasek9-mz.151-4.M12a(1).bin"


Last reload type: Normal Reload


<omitted>

Cisco 2811 (revision 1.0) with 512000K/12288K bytes of memory.
Processor board ID FHK1404F3U8
2 FastEthernet interfaces
1 Channelized E1/PRI port
DRAM configuration is 64 bits wide with parity enabled.
239K bytes of non-volatile configuration memory.
250368K bytes of ATA CompactFlash (Read/Write)

 

License Info:


License UDI:

-------------------------------------------------
Device#   PID                 SN
-------------------------------------------------
*0       CISCO2811             FHK1404F3U8   

Configuration register is 0x2102

 

Router#    config t

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#ip tcp ?
  RST-count           Configure RST throttle count
  async-mobility      Configure async-mobility
  chunk-size          TCP chunk size
  ecn                 Enable Explicit Congestion Notification
  mss                 TCP initial maximum segment size
  path-mtu-discovery  Enable path-MTU discovery on new TCP connections
  queuemax            Maximum queue of outgoing TCP packets
  selective-ack       Enable TCP selective-ACK
  synwait-time        Set time to wait on new TCP connections
  timestamp           Enable TCP timestamp option
  window-size         TCP window size

 

• Para routers ISR G2

Router#show ver

Cisco IOS® Software, C1900 Software (C1900-UNIVERSALK9-M), Version 15.4(3)M4, RELEASE SOFTWARE (fc1)

<omitted>

Router uptime is 1 minute
System returned to ROM by reload at 10:28:40 UTC Mon Oct 31 2016
System image file is "flash:c1900-universalk9-mz.SPA.154-3.M4.bin"
Last reload type: Normal Reload
Last reload reason: Reload Command

<omitted>

Cisco CISCO1941/K9 (revision 1.0) with 2543552K/77824K bytes of memory.
Processor board ID FHK141571QW
4 FastEthernet interfaces

<omitted>

Technology Package License Information for Module:'c1900'

 
------------------------------------------------------------------------
Technology    Technology-package                  Technology-package
              Current              Type           Next reboot 
------------------------------------------------------------------------
ipbase        ipbasek9             Permanent      ipbasek9
security      securityk9           RightToUse     securityk9
data          None                 None           None          
NtwkEss       None                 None           None


Configuration register is 0x2102


Router#    config t

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#ip tcp ?
  RST-count           Configure RST throttle count
  async-mobility      Configure async-mobility
  chunk-size          TCP chunk size
  ecn                 Enable Explicit Congestion Notification
  keepalive           Configure TCP Keepalive parameters
  mss                 TCP initial maximum segment size
  path-mtu-discovery  Enable path-MTU discovery on new TCP connections
  queuemax            Maximum queue of outgoing TCP packets
  selective-ack       Enable TCP selective-ACK
  synwait-time        Set time to wait on new TCP connections
  timestamp           Enable TCP timestamp option
  window-size         TCP window size

• Para routers ISR G3

Router#sh ver

Cisco IOS® XE Software, Version 03.15.02.S - Standard Support Release
Cisco IOS® Software, ISR Software (X86_64_LINUX_IOS® D-UNIVERSALK9-M), Version 15.5(2)S2, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2015 by Cisco Systems, Inc.
Compiled Fri 16-Oct-15 18:00 by mcpre

<omitted>

Router uptime is 7 minutes
Uptime for this control processor is 8 minutes
System returned to ROM by reload
System image file is "bootflash:isr4300-universalk9.03.15.02.S.155-2.S2-std.SPA.bin"
Last reload reason: Reload Command

<omitted>

Technology Package License Information: 

-----------------------------------------------------------------
Technology    Technology-package           Technology-package
              Current       Type           Next reboot 
------------------------------------------------------------------
appx             None             None             None            
uc               uck9             Permanent        uck9
security         securityk9       EvalRightToUse   securityk9
ipbase           ipbasek9         Permanent        ipbasek9

 

cisco ISR4331/K9 (1RU) processor with 1665776K/6147K bytes of memory.
Processor board ID FDO2012A0AT
3 Gigabit Ethernet interfaces
32768K bytes of non-volatile configuration memory.
4194304K bytes of physical memory.
3223551K bytes of flash memory at bootflash:.


Configuration register is 0x2102

 

Router#    config t

Enter configuration commands, one per line.  End with CNTL/Z.


Router(config)#ip tcp ?
  RST-count           Configure RST throttle count
  async-mobility      Configure async-mobility
  chunk-size          TCP chunk size
  ecn                 Enable Explicit Congestion Notification
  keepalive           Configure TCP Keepalive parameters
  mss                 TCP initial maximum segment size
  path-mtu-discovery  Enable path-MTU discovery on new TCP connections
  queuemax            Maximum queue of outgoing TCP packets
  selective-ack       Enable TCP selective-ACK
  synwait-time        Set time to wait on new TCP connections
  timestamp           Enable TCP timestamp option
  window-size         TCP window size 

• Para routers ASR1k

Router#show version

Cisco IOS® XE Software, Version 03.16.01a.S - Extended Support Release
Cisco IOS® Software, ASR1000 Software (X86_64_LINUX_IOSD-UNIVERSAL-M), Version 15.5(3)S1a, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2015 by Cisco Systems, Inc.
Compiled Wed 04-Nov-15 13:57 by mcpre

<omitted>

Router uptime is 1 minute
Uptime for this control processor is 2 minutes
System returned to ROM by reload
System image file is "bootflash:asr1001x-universal.03.16.01a.S.155-3.S1a-ext.SPA.bin"
Last reload reason: PowerOn

License Level: ipbase
License Type: Permanent
Next reload license Level: ipbase

cisco ASR1001-X (1NG) processor (revision 1NG) with 3753592K/6147K bytes of memory.
Processor board ID FXS1925Q33T
6 Gigabit Ethernet interfaces
2 Ten Gigabit Ethernet interfaces
32768K bytes of non-volatile configuration memory.
8388608K bytes of physical memory.
6684671K bytes of eUSB flash at bootflash:
 

Configuration register is 0x2102
Router#config t
Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#ip tcp ?
  RST-count           Configure RST throttle count
  async-mobility      Configure async-mobility
  chunk-size          TCP chunk size
  ecn                 Enable Explicit Congestion Notification
  keepalive           Configure TCP Keepalive parameters
  mss                 TCP initial maximum segment size
  path-mtu-discovery  Enable path-MTU discovery on new TCP connections
  queuemax            Maximum queue of outgoing TCP packets
  selective-ack       Enable TCP selective-ACK
  synwait-time        Set time to wait on new TCP connections
  timestamp           Enable TCP timestamp option
  window-size         TCP window size

Solución

Para habilitar la función TCP Intercept, necesitará:

• Mínimo de conjunto de funciones entbase en los routers ISR G1
• Appxk9/Datak9 en los routers de las series ISRG2 y G3
• Licencia mínima de servicios de asesoramiento en el router de la serie ASR1k

Una vez que habilita la licencia requerida en la plataforma, puede configurar lo mismo:

Router(config)#ip tcp ?
  RST-count           Configure RST throttle count
  async-mobility      Configure async-mobility
  chunk-size          TCP chunk size
  ecn                 Enable Explicit Congestion Notification
  intercept           Enable TCP intercepting
  keepalive           Configure TCP Keepalive parameters
  mss                 TCP initial maximum segment size
  path-mtu-discovery  Enable path-MTU discovery on new TCP connections
  queuemax            Maximum queue of outgoing TCP packets
  selective-ack       Enable TCP selective-ACK
  synwait-time        Set time to wait on new TCP connections
  timestamp           Enable TCP timestamp option
  window-size         TCP window size

Verificación

Actualmente, no hay un procedimiento de verificación disponible para esta configuración.

Troubleshoot

Actualmente, no hay información específica de troubleshooting disponible para esta configuración.

Información Relacionada

• http://www.cisco.com/c/en/us/td/docs/ios/12_2/security/configuration/guide/fsecur_c/scfdenl.html
• Soporte Técnico y Documentación - Cisco Systems