Configuration PAT (Destination NAT) and NAT on the Juniper SRX with two ISP connections for two DNS servers in the DMZ

Introduction.

We have two dns servers and Juniper SRX 220H cluster. Dns servers are in the DMZ zone. Juniper SRX cluster is connecting to two ISPs.
Task:
configure PAT and NAT that one DNS server works only through one ISP (one-to-one).

700

Solution.

1. Configure two security zones on the Juniper:

{primary:node1}[edit]
set security zones security-zone ISPs interfaces reth0.0
set security zones security-zone ISPs interfaces reth1.0
set security zones security-zone ISPs address-book address A_ISPs_DNS-1 IP_ISP-1/32  
set security zones security-zone ISPs address-book address A_ISPs_DNS-2 IP_ISP-2/32

set security zones security-zone DMZ interfaces reth2.0
set security zones security-zone DMZ address-book address A_DMZ_DNS-1 IP_DMZ_DNS-1/32  
set security zones security-zone DMZ address-book address A_DMZ_DNS-2 IP_DMZ_DNS-2/32  

2. Configure security policies

{primary:node1}[edit]
set security policies from zone DMZ to zone ISPs policy DMZ_to_ISPs match source-address A_DMZ_DNS-1 
set security policies from zone DMZ to zone ISPs policy DMZ_to_ISPs match source-address A_DMZ_DNS-2 
set security policies from zone DMZ to zone ISPs policy DMZ_to_ISPs match destination-address any 
set security policies from zone DMZ to zone ISPs policy DMZ_to_ISPs match application junos-dns-tcp 
set security policies from zone DMZ to zone ISPs policy DMZ_to_ISPs match application junos-dns-udp 
set security policies from zone DMZ to zone ISPs policy DMZ_to_ISPs then permit
set security policies from zone ISPs to zone DMZ policy ISPs_to_DMZ match source-address any 
set security policies from zone ISPs to zone DMZ policy ISPs_to_DMZ match destination-address A_ISPs_DNS-1 
set security policies from zone ISPs to zone DMZ policy ISPs_to_DMZ match destination-address A_ISPs_DNS-2 
set security policies from zone ISPs to zone DMZ policy ISPs_to_DMZ match application junos-dns-tcp
set security policies from zone ISPs to zone DMZ policy ISPs_to_DMZ match application junos-dns-udp
set security policies from zone ISPs to zone DMZ policy ISPs_to_DMZ then permit

3. Disable the DNS security alg (without one the second ISP will not work.)

{primary:node1}[edit]
set security alg dns disable

4. Configure two routing instance

{primary:node1}[edit]
set routing-instances INS_ISP-1 instance-type forwarding
set routing-instances INS_ISP-1 routing-options static route 0.0.0.0/0 next-hop IP_DG_ISP-1
set routing-instances INS_ISP-2 instance-type forwarding
set routing-instances INS_ISP-2 routing-options static route 0.0.0.0/0 next-hop IP_DG_ISP-2

5. Configure default routing

{primary:node1}[edit]
set routing-options static route 0.0.0.0/0 next-hop IP_DG_ISP-1
set routing-options static route 0.0.0.0/0 qualified-next-hop IP_DG_ISP-2 preference 100

6. Configure policy routing

 {primary:node1}[edit]
 set firewall family inet filter PRULE_ISP-2 term TERM1 from address IP_ISP-2/32
 set firewall family inet filter PRULE_ISP-2 term TERM1 then routing-instance INS_ISP-2
 set firewall family inet filter PRULE_ISP-2 term default then accept

7. Apply policy routing on a interface that is connected to ISP-1

 {primary:node1}[edit]
 set interfaces reth0 unit 0 family inet filter output PRULE_ISP-2

8. Configure PPROXY-ARP

 {primary:node1}[edit]
 set security nat proxy-arp interface reth0.0 address IP_ISP-1/32
 set security nat proxy-arp interface reth1.0 address IP_ISP-2/32

9. Configure PAT

{primary:node1}[edit]
set security nat destination pool DMZ_DNS-1 address IP_DMZ_DNS-1/32
set security nat destination pool DMZ_DNS-1 address port 53
set security nat destination pool DMZ_DNS-2 address IP_DMZ_DNS-2/32
set security nat destination pool DMZ_DNS-2 address port 53
set security nat destination rule-set ISPs_to_DMZ from zone ISPs
set security nat destination rule-set ISPs_to_DMZ rule PAT_DNS_1 match destination-address IP_ISP-1/32
set security nat destination rule-set ISPs_to_DMZ rule PAT_DNS_1 match destination-port 53
set security nat destination rule-set ISPs_to_DMZ rule PAT_DNS_1 then destination-nat pool DMZ_DNS-1
set security nat destination rule-set ISPs_to_DMZ rule PAT_DNS_2 match destination-address IP_ISP-2/32
set security nat destination rule-set ISPs_to_DMZ rule PAT_DNS_2 match destination-port 53
set security nat destination rule-set ISPs_to_DMZ rule PAT_DNS_2 then destination-nat pool DMZ_DNS-2

10. Configure NAT

{primary:node1}[edit]
set security nat source pool EXT_DNS-1 address IP_ISP-1/32
set security nat source pool EXT_DNS-2 address IP_ISP-2/32
set security nat source rule-set From_DMZ_to_ISPs from zone DMZ
set security nat source rule-set From_DMZ_to_ISPs to zone ISPs
set security nat source rule-set From_DMZ_to_IMT_IP rule NAT_DNS-1 match source-address IP_DMZ_DNS-1/32
set security nat source rule-set From_DMZ_to_IMT_IP rule NAT_DNS-1 then source-nat pool EXT_DNS-1
set security nat source rule-set From_DMZ_to_IMT_IP rule NAT_DNS-2 match source-address IP_DMZ_DNS-2/32
set security nat source rule-set From_DMZ_to_IMT_IP rule NAT_DNS-2 then source-nat pool EXT_DNS-2

11. Commit

{primary:node1}[edit]
commit
en/jobs/juniper_srx_pat_dns_2isp.txt · Last modified: 2013/01/05 23:40 by admin
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