Connectivity NA(P)T 3 Thomson Gateway NAT > NAT: Network Address Translation ("IP Masquerading") > NAPT: Network Address and Port Translation. презентация

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Слайд 2Connectivity NA(P)T

Слайд 3Thomson Gateway NAT
NAT: Network Address Translation ("IP Masquerading")
NAPT: Network Address and

Port Translation

Слайд 4Definition
NAT:
Maps IP addresses from one address realm to other
Provides transparent routing

(disparate address realms)
Characteristics:
Transparent address assignment
Transparent routing through address translation
ICMP error packet payload translation

Слайд 5Necessity
IPv4: 32 bits
Private networks 10.0.0.0, 172.16.0.0, 192.168.0.0
LAN: inside IP addresses
WAN: outside

IP addresses

Слайд 6Example
[IN] eth0-> : 40.0.1.1 100.0.1.1

0076 TCP 10000->50000 [S.....]
[UT] eth0->pppoe0 : 50.50.1.1 100.0.1.1 0076 TCP 49125->50000 [S.....]

[IN] pppoe0-> : 100.0.1.1 50.50.1.1 0076 TCP 50000->49125 [S.A...]
[UT] pppoe0->eth0 : 100.0.1.1 40.0.1.1 0076 TCP 50000->10000 [S.A...]

[IN] eth0-> : 40.0.1.1 100.0.1.1 0076 TCP 10000->50000 [..A...]
[UT] eth0->pppoe0 : 50.50.1.1 100.0.1.1 0076 TCP 49125->50000 [..A...]


[nat]=>maplist
Idx Type Interface Outside Address Inside Address Use
1 NAPT pppoe0 50.50.1.1 40.0.1.1 1

40.0.1.1

PPPoE Server
100.0.1.1

Packet
flow

Session flow

Address binding

NAPT: extension of NAT

Слайд 7Static vs. Dynamic NAT
Static Address Assignment → Static NAT
One-to-one address mapping
Fixed

in time
Dynamic Address Assignment → Dynamic NAT
Based on usage requirements and session flow
Binding used and re-used

Слайд 8Basic NAT
Block external addresses set aside for translation
For sessions originating in

private domain
Example
Static
Idx Type Interface Outside Address Inside Address
1 NAT ipoa0 50.0.0.138 unmapped
Access List................... 10.0.0.10 Foreign Address............... any
Protocol...................... any
Flags......................... Static Description................... Outbound Basic NAT

Слайд 9When to Use Basic NAT
Inside address not routable on outside network
Hiding

inside addresses from outside world
Avoid network renumbering when changing service provider

Слайд 10NAPT
Extension: translation of transport identifiers
TCP, UDP: port numbers
ICMP: query identifiers
Allows sharing

single external address
Idx Type Interface Outside Address Inside Address Use
1 NAPT ipoa0 50.0.0.138 unmapped 2
Access List................... 40.0.0.0/16
Foreign Address............... any
Protocol...................... any
Flags......................... Static
Description................... Outbound NAPT without defserver

Слайд 11NAPT – Continued
NAPT uses ports from range [49125 - 65536]

[IN] eth0->

: 40.0.1.1 100.0.1.1 0076 TCP 10000->50000 [S.....]
[UT] eth0->ipoa0 : 50.0.1.138 100.0.1.1 0076 TCP 49125->50000 [S.....]
[IN] ipoa0-> : 100.0.1.1 50.0.1.138 0076 TCP 50000->49125 [S.A...]
[UT] ipoa0->eth0 : 100.0.1.1 40.0.1.1 0076 TCP 50000->10000 [S.A...]
[IN] eth0-> : 40.0.1.1 100.0.1.1 0076 TCP 10000->50000 [..A...]
[UT] eth0->ipoa0 : 50.0.1.138 100.0.1.1 0076 TCP 49125->50000 [..A...]

[IN] eth0-> : 40.0.1.2 100.0.1.1 0076 TCP 10001->50000 [S.....]
[UT] eth0->ipoa0 : 50.0.1.138 100.0.1.1 0076 TCP 49126->50000 [S.....]
[IN] ipoa0-> : 100.0.1.1 50.0.1.138 0076 TCP 50000->49126 [S.A...]
[UT] ipoa0->eth0 : 100.0.1.1 40.0.1.2 0076 TCP 50000->10001 [S.A...]
[IN] eth0-> : 40.0.1.2 100.0.1.1 0076 TCP 10001->50000 [..A...]
[UT] eth0->ipoa0 : 50.0.1.138 100.0.1.1 0076 TCP 49126->50000 [..A...]


Слайд 12When to Use NAPT
Multiple private hosts accessing public network through same

gateway
Link specific traffic to private host
Redirect all unknown incoming traffic to chosen private host

Слайд 13Two-Way NAT
Sessions can be initiated from host both in public as

in private network
Used to make private servers available on Internet
Examples:
Static
Idx Type Interface Outside Address Inside Address Use
1 NAT pppoe0 50.0.0.138 40.0.1.1 0
Access List................... 40.0.1.1
Foreign Address............... any
Protocol...................... any
Flags......................... Static
Description................... Two-way NAT

[IN]pppoe0-> : 100.0.1.1 50.0.0.138 0076 TCP 50000->10000 [S.....]
[UT]pppoe0->eth0 : 100.0.1.1 40.0.1.1 0076 TCP 50000->10000 [S.....]
[IN] eth0-> : 40.0.1.1 100.0.1.1 0076 TCP 10000->50000 [S.A...]
[UT] eth0->pppoe0 : 50.0.0.138 100.0.1.1 0076 TCP 10000->50000 [S.A...]

Слайд 14Connection Sharing HyperNAT – IP Passthrough
Allow public IP address to be used

on LAN
“Default server”
IPSeC-AH client
Any NAT issues …
While preserving NAPT access for other PCs
UPnP v1.0
All known alg’s : IPsec, pptp/l2tp, sip, …
Public IP address
assigned to PC manually or via DHCP
continued 1-1 NAT routing during WAN IP address change event
Compatible with dial-on-demand !


Слайд 15Connection Sharing HyperNAT – IP Passthrough
“Default Server”
Service/Portmaps

Слайд 16Connectivity – NAT ALGs

Слайд 17Definition
ALG = Application Level Gateway
Translates addresses and ports NAT engine cannot

handle
“Opens firewall”
Creates NAT mappings

Слайд 18ALG Intervention Level
NAPT
ALG

Слайд 19ALGs Real Actions
Create connection
Delete connection
Search connection
Packet modification
Add NAT mapping
Remove NAT mapping

Слайд 20Supported ALGs
IP6to4
PPTP (VPN)
ESP (IPSec)
IKE (IPSec)
SIP (VoIP)
JABBER
CU/SeeMe

RAUDIO
RTSP
ILS (NetMeeting phonebook)
H245 (NetMeeting)
H323 (NetMeeting)
IRC
FTP

Слайд 21ALGs Triggering
Each ALG is bound to (range of) port(s)

{Administrator}[connection]=>applist
Application Proto

DefaultPort Traces Timeout
IP6TO4 6to4 0 enabled unavailable
PPTP tcp 1723 enabled unavailable
ESP esp 0 unavailable 15' 0"
IKE udp 500 disabled 15' 0"
SIP udp 5060 disabled 6 0"
JABBER tcp 5222 disabled 2' 0"
CU/SeeMe udp 7648 enabled unavailable
RAUDIO(PNA) tcp 7070 enabled unavailable
RTSP tcp 554 enabled unavailable
ILS tcp 389 unavailable 5' 0"
H245 tcp 0 unavailable 5' 0"
H323 tcp 1720 enabled unavailable
IRC tcp 6667 enabled 5' 0"
LOOSE(UDP) udp 0 enabled 5' 0"
FTP tcp 21 enabled unavailable

Available ALGs:

Слайд 22FTP ALG
No firewall opening needed
Firewall must accept incoming connection on port

1027, coming from port 2024 → inbound port shift mapping must be present

LAN

WAN

Tests:
Inbound vs. outbound
One vs. multiple LAN clients
One vs. multiple WAN servers
LAN server

Слайд 23Managed Security Service Firewall

Слайд 24Managed Security Service Firewall - Overview
Firewall has 2 functions
Protect ST Gateway

from unwanted management access
Police traffic LAN to WAN and vice versa

Mapped on 2 Fwall services
Firewall (fwd)
GUI/CLI
ServiceManager (sink/src)
CLI

Слайд 25Managed Security Service Firewall - Default Policies

Edit Level

Слайд 26Stateful firewall CLI configuration
General configuration
:firewall config

state
Tcpchecks
Udpchecks
Icmpchecks


Слайд 27Stateful firewall CLI configuration
Firewall menu
Chain
Incoming data is ‘intercepted’ at packet interception

points with chains attached to them
List : shows available chains
Sink and source chains manages data sent/received to/from CPE ‘host’.
Sink/source traffic controlled by hostmanager
Rule
Every chain can have a set of rules, each with an index.
Lowest index rules are executed first



Слайд 28Data Flow overview
Service MANAGER
HOST SERVICES
SYSTEM SERVICES
Manual firewall rules

Слайд 29Firewall levels
Only related to forward chain !


Слайд 30Firewall rules
Rules are linked to chains.
Main actions : drop, accept, deny,

count
Classification criteria
Source and destination interface
Source and destination IP
Service :
Services from the :expr menu
Manual expressions can be created
Classifiers :
Tos, precedence, proto, dscp
Source/destination port ranges

Слайд 31Firewall rules
Example with level=disabled

Слайд 32Firewall level
Different levels according ICSA specification
Set, check level :
Firewall level set

Слайд 33Hands on - Firewall
Create a rule which drops http forwarding if

the level of the firewall is set to Standard.
:firewall level set …
:firewall rule add
chain forward_level
…
Create a rule which drops ftp to the CPE.
:firewall rule add
chain sink
…
Create a rule which denies udp with dest port 666 initiated from the CPE
:expr add
type serv
…
:firewall rule add
chain source
…
ip debug sendto addr=192.168.2.1 dstport=666

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